A helmet may save you life in a motorcycle/ATV/headbanging accident, but that doesn't mean you'll be in any condition to call for help. The Wireless Impact Guardian is a helmet that takes such an accident into account and contacts 911 for you.
Loading with the placement on your head, GPS tracks your position while a 3G transponder waits in the ready. If the accelerometers sense an impact, the helmet will beep for a minute. If the beeping is not stopped, it calls for help. Currently going through the patent process, let's hope to see this on shelves sooner rather than later. [UM via textually]