I’ve owned a good many HP calculators in my day and still prefer my venerable HP41C over the many more modern calculators I own.  But I’m ready to buy an HP 20b Financial calculator. Why do I want a financial calculator? I don’t.

It turns out though that HP has released the entire development package for the calculator hardware (here

Washington Heights release

). So you can reprogram the calculator any way that you like. There’s even a Wiki

with details.

So for about US$40 you get an Atmel 32-bit arm processor running at 30MHz connected (portably) to a nice LCD display and a keyboard. You need a JTAG adapter and some free software and you are good to go.