PocketStation Tech Page
I don't know that much about this glorified memory card, but there are resources available that have information and tools to adequitely do the job.  Amateur developers rejoice!  Here's a quick rundown of the Pocketstation, and a good link to get you all started...



Pocketstation Specs: (from 420 Studios pocketstation page)

CPU : ARM7T 32-bit Reduced Instruction Set Chip (RISC) Processor
Graphics : 32x32x1 resolution LCD
Sound : 12 bit PCM
Memory : SRAM 2k, FlashRAM 128k
BiDirectional IR port
4 directional buttons and 1 fire button.
Runs off of 1 CR 2032 Lithium Battery
Plugs into Playstation Memory Slot
Selling price : ~$26 / 3000 yen 



General development with public domain code and emulators:

420 Studios