So for a while I have been kicking around the idea of having an accelerometer embedded in the helmet to record trauma. I feel that this is an invaluable piece of technology to incorporated into helmet because it may be able help determine if the person wearing the helmet has experienced G forces that could result in a brain injury. In instances where the helmet takes non-destructive impacts it could be used to determine if the helmet needs to be replaced, since it is often difficult if not impossible to tell if the integrity of a helmet has been compromised unless the amage is visible.
http://www.isthq.com/main.asp?a=9989&b=269aba22083db07c5e5e50efeea04ba103520b77&pageid=165&view=active

These devices record g forces applied to an object are cheap enough to be disposable.

"The Shock Timer-Plus 3Dtm is a low cost, low g, 3-axis shock detector with time stamp. The device detects and logs whenever shocks occur that exceed the trip level, and saves a date and time stamp of occurrence and peak-g level. The device is re-settable and reusable via a wireless IRDA interface to a PC. The unit is supplied with a simple windows software package for setting it up, extracting data, and writing it to a file. The file may then be opened in MS Excel for review and analysis"

This is gold!