> Solution: light-up accelerometer helmets, and a new rule that if the helmet lights up it's a penalty

I like this idea.

Many motorsports (such as Formula 1) have safety accelerometers that require medical checkup to the driver when tripped (I think around 25-50 G impacts). It also alerts the track officials to take special care if the driver has to be extricated from the vehicle. There have been incidents in the past when a driver has walked away from the crash, but later developed a headache and died in the following days.