Isn't the new spot coming out with the text message app for smart phones?
Ya the do right now but not as convienient and your messages cant be sent to individuals just your group. The other draw back is you can only send 41 characters instead of 160. Couldnt find on the web site where it says that the SPOT communicator can be used on its own either so if it can as I see no buttons on it you are in total reliability of your phone battery.
Quoted from the SPOT web site,
Use Type & Send to create custom messages:
•Send up to 41 characters in a message
•Messages will be sent directly to the contact groups you select via email or SMS
•Post custom messages on Twitter, Facebook – and with the DeLorme PN-60w with SPOT Communicator, even post to Geocaching.com
•If you encounter problems, you can send SOS messages describing your situation
Type & Send Message Delivery
When you send a Type & Send Message, you are sending one message to a Contact Group. Whether you have one person or 50 people in that contact group, you are only charged for one message. In other words, you only get charged for each time you send a Type & Send message, not by how many people it gets delivered to.