How do you write to the sdcard while its packed in its foam helmet? If you put a little computer in there then it would have more mass and metal to smash around on impact. Maybe like a tiny usb card reader and a long data cable?

I wonder if running the data cable through the foam would cause problems like letting fire/fuel/water through the helmet and disolve/melt the plastics or if you whip a cable hard enough it can cut right through things like a weed wacker.