I’m interested in keeping my hands on the home row. This is going to be a bigger deal when I mount the 2 halves of a split keyboard at my sides, so my hands will be too far away from the desk to use the mouse.
There are led-based tracking systems, usually infra red. These seem to require custom computer software. Other software I tested uses a webcam, but is quite slow.
I have found an interesting approach here.
It uses an Arduino with a gyro and accelerometer breakout board. I think with a Leonardo board, or similar, the design could be simplified (no USB chip). Also, Adafruit offers a LSM9DS0 breakout board with the logic level converter built in.
Since the Leonardo-type boards can do a usb hid mouse and a serial connection at the same time, we don’t even need a button, just an app on the host to ping once in a while to tell it to recenter, in case of gyro drift. In this case, the resistor wouldn’t be needed either.
That leaves 2 parts total. Also the Leonardo can be swapped out for something tiny with the same mcu.
I don’t need to completely replace the mouse, but it would be nice to take breaks from it while standing if possible.