RepayingBristol, EnglandBorrower approvedListed Mar 14, 2026
PiWalletSV: an air-gapped wallet built from parts you can buy
A kit batch and an injection-moulding tool for the Raspberry Pi hardware wallet that never touches a network.
A kit batch and an injection-moulding tool for the Raspberry Pi hardware wallet that never touches a network.
Every hardware wallet asks you to trust a black box. PiWalletSV asks you to trust a Raspberry Pi, a screen and a camera, with no Wi-Fi, no Bluetooth and no Ethernet. A companion app in an ordinary browser ferries transactions across the air gap as animated QR codes; the Pi just signs. The companion never sees more than the public xpub and a pre-signed transaction.
The part that makes it more than a novelty is what happens before the signature. Every input the companion proposes is cryptographically re-verified on the device itself, against BEEF proofs anchored to block headers the Pi displays to you, so a compromised laptop cannot talk the signer into approving something that is not there. No signed firmware, no proprietary hardware, no update server that can brick the device or push a backdoor next quarter: you write the SD card, you read the source, you keep the parts.
The project has sold in limited batches, hand-assembled, full kit or case-only, card or BSV. The case is 3D-printed one at a time, and that is the constraint this loan removes: an injection-moulding tool takes it from forty minutes of printing to eleven seconds, which is the difference between a project and a product.
Proceeds fund the tool and a 900-kit batch. Repaid monthly from kit sales, secured on the tool and the stock.
Four limited batches, all cleared, with a waiting list that has not been under 300 people since 2025.
Case cost falls by 84% and lead time by two orders of magnitude. It is a capital cost that permanently changes unit economics.
The wire format, the QR transport, the derivation rules and the SPV requirements are all published, so anyone can build a compatible signer. People buy the kit anyway, which is the strongest demand signal the project has.
Tool commissioneddone
Toolmaker engaged and paid.
May 2, 2026
First shots
Initial mouldings for fit testing.
Sep 12, 2026
Batch assembled
900 kits built and QA'd.
Jan 30, 2027
Batch sold through
Waiting list cleared.
Aug 1, 2027
Abhi Sridharan
Independent reviewerCredit analyst, 11 years across SME lending, supply-chain finance and early-stage software.
Grade
Proven demand, honest founders, and a capital purchase that genuinely changes the cost base. The tool's zero resale value is the reason this is not an A.
Four sold-out batches and a standing waiting list of 300+ is about as clean a demand signal as a hardware project of this size can produce. The moulding tool takes case cost from £18 to under £3 and lead time from forty minutes to eleven seconds. That is a real change, not a margin tweak.
The problem is what the collateral is worth on a bad day. A first charge over a bespoke tool for one product's case is a charge over scrap metal if the product stops selling. The capped personal guarantee is doing more work here than the charge is, and lenders should read it that way.
The beta firmware label is not a formality. This is a device whose single job is to hold keys offline, and the project says openly that the software is beta. I asked about this. The answer, that they will not drop the label until an independent review is funded, which this loan does not pay for, is the right answer and it is also a risk that stays live for the whole term.
Posted Mar 14, 2026
| # | Due | Principal | Interest | Total | Status | Transaction |
|---|---|---|---|---|---|---|
| 1 | May 15, 2026 | 1,960 MNEE | 391.96 MNEE | 2,352 MNEE | Paid |
PiWallet Collective Ltd · Consumer hardware · Bristol, England · founded 2024
An air-gapped wallet for Bitcoin SV, built on a Raspberry Pi with a screen and a camera and no radio of any kind. Transactions cross the gap as QR codes. Off-the-shelf parts, an open spec, and a vault you can back up to a USB stick: sold as a full kit or as the case alone.
Ade Fowler
Hardware
Sunny Ghattaora
Firmware
If demand does not materialise, an injection-moulding tool for a specific case has close to no resale value.
The firmware is still labelled beta. A serious key-handling defect would end sales immediately.
The base unit has been supply-constrained twice in five years. A third episode would stall the batch.
Collateral coverage
0.98×
$38,600 of security against $39,196 still outstanding. The line is one times.
How it was marked. Kit inventory at 60% of trade. The injection-moulding tool at 20% of cost: a bespoke tool for one product's case is worth scrap if the product stops selling. Marked Mar 19, 2026 by Abhi Sridharan.
A mark on a date, not a valuation and not a promise. Nothing here can be sold at 3am: enforcing a charge over stock or receivables takes months, costs money, and recovers less than the figure above.
A missed instalment moves the loan to late. If it is not cured or restructured by the next due date it moves to default and arbitration opens automatically. Every lender with a position can read the case file, add evidence and vote on the recovery route, weighted by principal.
How arbitration worksNobody gets excited about a mould. But the case is 84% of our per-unit cost above the Pi itself, and going from forty minutes of printing to eleven seconds is what turns a project people admire into a product people can buy. First shots the second week of September.
The toolmaker started cutting in July. First shots expected the second week of September, then a fortnight of fit testing before we commit the batch. Component orders for the 900 kits are placed and staged.
Thank you. We opened the waiting list to lenders first as promised and it went from 310 to 460 inside a week, which is more than half the batch spoken for before the tool exists.
Some updates on this loan are visible only to lenders holding a position. They are withheld on the server, not hidden in your browser.
What the borrower answered before the listing went up, and everything asked since. Anyone can read this; anyone with a wallet connected can ask.
Every live loan has a room where lenders and the borrower talk. Anyone can read it; anyone holding a position can post. The thread above is the public one and stays public.
Open lender chatAnd 184 more. This build models a handful of lenders as people with profiles and carries the rest as a count, so the list above is a subset of the book rather than all of it.
Every lend and every repayment on this loan.
| Who | What | Amount | When | Transaction |
|---|---|---|---|---|
| @ade.f | Instalment 4 of 24 | 2,380 MNEE | 14d ago | 4d4422…b9bb |
#1 May 15, 2026 1,960 MNEE principal 391.96 MNEE Paid |
| 2 | Jun 15, 2026 | 1,960 MNEE | 375.63 MNEE | 2,335 MNEE | Paid | bde4ef…9c58 |
#2 Jun 15, 2026 1,960 MNEE principal 375.63 MNEE Paid | ||||||
| 3 | Jul 15, 2026 | 1,960 MNEE | 359.30 MNEE | 2,319 MNEE | Paid | bee4f1…1edc |
#3 Jul 15, 2026 1,960 MNEE principal 359.30 MNEE Paid | ||||||
| 4 | Aug 15, 2026 | 1,960 MNEE | 342.96 MNEE | 2,303 MNEE | Paid | bfe4f2…a160 |
#4 Aug 15, 2026 1,960 MNEE principal 342.96 MNEE Paid | ||||||
| 5 | Sep 15, 2026 | 1,960 MNEE | 326.63 MNEE | 2,286 MNEE | Scheduled | – |
#5 Sep 15, 2026 1,960 MNEE principal 326.63 MNEE Scheduled | ||||||
| 6 | Oct 15, 2026 | 1,960 MNEE | 310.30 MNEE | 2,270 MNEE | Scheduled | – |
#6 Oct 15, 2026 1,960 MNEE principal 310.30 MNEE Scheduled | ||||||
| 7 | Nov 15, 2026 | 1,960 MNEE | 293.97 MNEE | 2,254 MNEE | Scheduled | – |
#7 Nov 15, 2026 1,960 MNEE principal 293.97 MNEE Scheduled | ||||||
| 8 | Dec 15, 2026 | 1,960 MNEE | 277.64 MNEE | 2,237 MNEE | Scheduled | – |
#8 Dec 15, 2026 1,960 MNEE principal 277.64 MNEE Scheduled | ||||||
| 9 | Jan 15, 2027 | 1,960 MNEE | 261.31 MNEE | 2,221 MNEE | Scheduled | – |
#9 Jan 15, 2027 1,960 MNEE principal 261.31 MNEE Scheduled | ||||||
| 10 | Feb 15, 2027 | 1,960 MNEE | 244.97 MNEE | 2,205 MNEE | Scheduled | – |
#10 Feb 15, 2027 1,960 MNEE principal 244.97 MNEE Scheduled | ||||||
| 11 | Mar 15, 2027 | 1,960 MNEE | 228.64 MNEE | 2,188 MNEE | Scheduled | – |
#11 Mar 15, 2027 1,960 MNEE principal 228.64 MNEE Scheduled | ||||||
| 12 | Apr 15, 2027 | 1,960 MNEE | 212.31 MNEE | 2,172 MNEE | Scheduled | – |
#12 Apr 15, 2027 1,960 MNEE principal 212.31 MNEE Scheduled | ||||||
| 13 | May 15, 2027 | 1,960 MNEE | 195.98 MNEE | 2,156 MNEE | Scheduled | – |
#13 May 15, 2027 1,960 MNEE principal 195.98 MNEE Scheduled | ||||||
| 14 | Jun 15, 2027 | 1,960 MNEE | 179.65 MNEE | 2,139 MNEE | Scheduled | – |
#14 Jun 15, 2027 1,960 MNEE principal 179.65 MNEE Scheduled | ||||||
| 15 | Jul 15, 2027 | 1,960 MNEE | 163.32 MNEE | 2,123 MNEE | Scheduled | – |
#15 Jul 15, 2027 1,960 MNEE principal 163.32 MNEE Scheduled | ||||||
| 16 | Aug 15, 2027 | 1,960 MNEE | 146.98 MNEE | 2,107 MNEE | Scheduled | – |
#16 Aug 15, 2027 1,960 MNEE principal 146.98 MNEE Scheduled | ||||||
| 17 | Sep 15, 2027 | 1,960 MNEE | 130.65 MNEE | 2,090 MNEE | Scheduled | – |
#17 Sep 15, 2027 1,960 MNEE principal 130.65 MNEE Scheduled | ||||||
| 18 | Oct 15, 2027 | 1,960 MNEE | 114.32 MNEE | 2,074 MNEE | Scheduled | – |
#18 Oct 15, 2027 1,960 MNEE principal 114.32 MNEE Scheduled | ||||||
| 19 | Nov 15, 2027 | 1,960 MNEE | 97.99 MNEE | 2,058 MNEE | Scheduled | – |
#19 Nov 15, 2027 1,960 MNEE principal 97.99 MNEE Scheduled | ||||||
| 20 | Dec 15, 2027 | 1,960 MNEE | 81.66 MNEE | 2,041 MNEE | Scheduled | – |
#20 Dec 15, 2027 1,960 MNEE principal 81.66 MNEE Scheduled | ||||||
| 21 | Jan 15, 2028 | 1,960 MNEE | 65.33 MNEE | 2,025 MNEE | Scheduled | – |
#21 Jan 15, 2028 1,960 MNEE principal 65.33 MNEE Scheduled | ||||||
| 22 | Feb 15, 2028 | 1,960 MNEE | 48.99 MNEE | 2,009 MNEE | Scheduled | – |
#22 Feb 15, 2028 1,960 MNEE principal 48.99 MNEE Scheduled | ||||||
| 23 | Mar 15, 2028 | 1,960 MNEE | 32.66 MNEE | 1,992 MNEE | Scheduled | – |
#23 Mar 15, 2028 1,960 MNEE principal 32.66 MNEE Scheduled | ||||||
| 24 | Apr 15, 2028 | 1,960 MNEE | 16.33 MNEE | 1,976 MNEE | Scheduled | – |
#24 Apr 15, 2028 1,960 MNEE principal 16.33 MNEE Scheduled | ||||||
Principal is repaid in MNEE; the coupon is paid in MNEE, which is the same token, so an instalment has a single total. Every settled instalment carries the transaction that paid it.
