MaxDolensky, if a keyOn command is sent on the release of a button, how would a keyOff command be sent? Happy to develop this with you.
Adzetko, I selected the Stm brand for a couple of reasons, the development suite is free for code size under 32k, the programming hardware is cheap and clones are available and last, it is the most common ARM brand found in cheap eBay crap which opens up a world of hacking options.
I chose the STM32F103 because it was used in the 32bit arduino clones which provides a devkit at a very low price. It has an enormous set of inbuilt peripherals including a hadware USB engine.
Im using this same MCU to run my beetles engine management. Very powerful and versatile.
It is mostly 5v tolerant which is rare on a 32bit mcu, runs at 72mhz and is stable overclocked to 107mhz and it is cheap!
If you want one suitable for development, I'd suggest the itead maple. It is cheap and has the same footprint as an arduino which seems popular here. Get a Stlink from eBay to program it.