Let the hive mind of Engadget get that for you.
"I'm in the market for a new phone and money isn't a limitation. I'm also not partial to any particular US carrier, but here are some of the features I'd like to have: WiFi, GPS, good coverage in lots of places, push Gmail (a must!), physical keyboard (a must!), a touchscreen, decent battery life and a relatively slim body. And please, nothing that has a fruit logo on it. No offense to the fruit fans, though. Thanks!"
Just one thing: The service is to be used in NON-emergency situations (as reported by Textually.org), not during emergencies as mentioned in your post. As far as I am aware, carriers are not guaranteeing SMS delivery times. So, it wouldn't do any good if the text for help reaches the police hours after the incident.