After measuring my posture without feedback and after with bluetooth notification feedback I'm pretty happy with the result of this project. Here are the improvements I would include in another revision of the board:

1) Vibration motor for non-bluetooth posture notifcations

2) Add traces/connector for ICSP (CRITICAL!)

3) Replace R1 to 2k to increase charge rate to 500 mA

It would be neat to do a study of long term impacts of using this, could it actually improve sitting/standing posture without the notifications? I think that it likely would.

Here are some measurements before and after enabling notifications