The Proof
of Concept
I started by researching European payment institutions to see how we could "follow the rules." But I soon realized an uncomfortable truth: it is naive to think that the traditional financial system is going to give us the tools that would make it disappear.
If they don't give us an API, we will use their notifications. This PoC demonstrates that a simple Raspberry Pi with a SIM module can "listen" to a Bizum and use that signal to release funds. If I, who had to learn Python along the way, have been able to build this, anyone can do it.
Components
| Component | Cost |
|---|---|
| Raspberry Pi 5 4GB | €93.82 |
| LUCKFOX 4G Hat — SIM7600E-H | €75.99 |
| 15.6" Portable Monitor | €63.42 |
| Micro HDMI Adapter | €5.00 |
| Thermal Paste | €6.55 |
| Heat sink (reused) | €0 |
| Case (reused) | €0 |
| Total | €244.78 |
First testnet transaction
A Bizum SMS arrived at the SIM number. The script parsed it, calculated the BCH amount at the real-time exchange rate, signed the transaction offline, and broadcasted it to the network. The whole process happened in seconds.
What is this actually for?
Automated Escrow
This hardware acts as a trusted third party. It can hold Bitcoin Cash in escrow until the operation is complete, releasing funds only when all parties fulfill their part of the deal. If something fails, the process is reversed and the deposit is automatically returned.
No bank permission required
It proves that we don't need the bank to open its doors to us. We use their own notification system to trigger smart contracts or simple transactions on the Bitcoin Cash network. Everything happens automatically, without the user needing special knowledge.