My trinkets arrived so I just had to try out a couple of things that I had running on an 8MHz mini pro clone.

My transmit unit uses the softseral function but won't work on my 12 MHz trinket. I guess I'll use hardware serial.

My code that boots up a GameBoy Advance works with no modification. I'm also working on a display unit that will be more "pocketable". I'll probably have a couple of different versions with different displays.