Here is another way to go about this:
Look on eBay for the "VeriFone VX510" credit card machine. This machine is obsolete and consistently under 50 bucks used, and it can download software at least three ways: 1) RS232 through a win32 command-line loader 2) through its dialup modem (same protocol as RS232 loader) 3) it can copy the programming from another terminal using a crossover serial cable.
I can compile for this platform, and it also has a printer so it can spit out e.g. paper wallets and transaction logs. I have already demonstrated the printer can print QR codes.
These things have tiny amounts of memory... if someone had written the verification code in C where its dependencies were minimal (e.g. relevant crypto code clipped out of openssl so it didn't depend on any external libs, and of course it can and should talk to a serial port) I could easily compile for this thing.
No need for an entire credit card machine. And $50 is way more than this thing costs.
Also, the thing about this machine is it's supposed to be easy. No need for rs232, command lines or reflashing old hardware. If you want to install the software on a credit card machine, be my guest, it's just not where I'm headed.