The Spot Messenger has always intrigued me a little bit. It's basically a portable ELT allowing you to call for help with the push of a button rather than a crash... You can chose folks to view your progress on google maps, or even have them get updates via text message. Additionally if you just need help, like a mechanic and not a paramedic, there's a button to ask for that.
While this certainly isn't a replacement for an ELT in your aircraft, it could be a useful tool for you backcountry folks to keep in the ole safety vest. Check out the video below from Wired detailing their test of the service. It's $169 to buy and about $100 a year to keep the service active making it one of the cheaper additions to your lifesaving kit! If you've carried a Spot and had the chance to use it, we'd love to hear about it in the comments.