The Teensy++ has me thinking this must be something with a huge config file, which needs that board’s larger RAM. I mean, they’re pricey compared to regular Teensy 2. But maybe you just had one lying around.
Is this for leaning in a game like Rainbow 6 Siege? I love to see the overlap between what were one tools created for accessibility and "DIY high performance" gaming. I purchased a footpedal from a retired piece of medical equipment, but I haven't gotten around to making it useful.
I mostly play CSGO or RTS games now, so I don't need additional buttons like I used to, but this is a really practical way to use cheap off the shelf parts and still get the spacing right.