Since the app is intended to be used while sleeping, it would be pretty easy to include a preprogrammed address in the 911 message (perhaps with a geolocation 'sanity check' just in case the wearer is traveling).

I think notifying a friend or family member is probably the most important thing. They can follow up from there.

Text-to-911 is growing in availability (in the US, anyway), but it's far from universal:

http://transition.fcc.gov/pshs/911/Text_911_Deployments.pdf

I just lost a really close friend about three weeks ago to epilepsy. He had a massive seizure and died in his sleep. His roommate found him next to his bed the next morning. I can't help but think about how his death could have been avoided, so I absolutely see the value in this feature. As far as I can tell, notifications would be THE feature of a system like this.