I'm creating an open hardware mouse that actually fits me! It's still not open and it's got way, WAY too much work ahead (design the PCB(s), design switch mounts in the model, add mouse support to ZMK, re-design the PCB cause I fucked up, make the top out of CNCed wood and the bottom out of milky transparent 3D printed resin)
Ive actually really wanted to do something like this as well I am just missing a few key pieces of information like how to go about aligning and sourcing a sensor and then the programming. Ive done my own keyboard and macro pad with an embedded AT32U4 and that project came out really well
I asked for 2 samples from pixart. After signing the NDA the gave me datasheets n all. It describes in great detail how it should be positioned and how it works - at least from what I saw. I've not yet messed with it.
Thats incredibly cool!