For simplicity, an LED is used to indicate if the acceleration threshold has been passed. One design decision I've been contemplating is adding a small radio so that trainers and doctors can immediately determine if a concussion has occurred. This will reduce the battery life, increase the cost, and increase the complexity though. I would also probably have to switch from the ATTiny85 to something like CC430 that has a microcontroller and radio built in if I didn't want to grow the size much. So I'm not sure if I'll do that or not. Maybe I'll make two versions, one with a radio and one without and see which works better.
I still need to build the programming/data download jig. This will probably be a little 3D printed, hinged thing with pogo pins on it so the device can be clamped down in it.
There's also a functional problem I need to fix in the current iteration. The accelerometer changes the impedance of the lines going into the ATTiny85 for programming, which means you can't both program the chip and have the accelerometer populated. You have to first populate the Tiny, program it, and then populate the accelerometer. So I need to play around a bit to fix that design problem.