I've been thinking, and have come to the conclusion that TimerSpy only needs to do 3 things well, software wise:
And ideally run #enSweepen [gd0096] and Visual Studio (Code), but that's of lesser importance. Essentially, it's the kind of applications that would run on a 1990/2000s PDA. I need some wireless connectivity like WiFi or BlueTooth for synchronisation, but I shouldn't need the power of a CB1 or CM4 to run those 3 main applications.
Along with a microcontroller, I was thinking of using the frontlit 3.2" memory LCD from Digikey but that was out of stock. There are £42 frontlit 2.7" ones, but AliExpress has a nonlit version for £17. I think I can just add some LEDs on each side, and could potentially look cooler than the frontlit version.
With the main requirements in mind, I'm thinking of trying to have everything, including the battery, fit on the back of my hand. I still haven't come up with a solution that allows for a Thumb1 Tetrinsic, nor do I have a mounting solution, so I'm going to allow for a solution that uses the thumb to hold TimerSpy in place.