I would also be concerned (this seems to be an extreme edge case) that off-roading may trip the sensor. I try not to break my equipment, but I've seen some guys running their daily driver pretty hard, and it's not uncommon to have some extreme jarring going on if you hit a jump wrong or run over a log going a bit too fast. I can see a good deal of this functionality from the device being applicable even off the road, but having 911 pay you a visit down in a mud pit because your tire hit a rock and bounced off doesn't seem like a positive.
"If you use Crash Alert, in the event you are in a crash, we may share your location and personally identifiable information with emergency responders and your emergency contacts."[1]
> Automatic uses your phone's data connection to immediately report the crash to 911 with your name, location, and vehicle description.