I bought a spot because it is one of the neatest gadgets I've seen. After using it a couple of times I discovered some quirks, however. The one I don't like is that you can't send an OK message while in tracking mode. For anybody to track you live you must give them access to your account ID and password. The account data base has personal info. That person also may make changes just as if he/she were you. It's ok if its a very trusted party.
SPOT has a "view only" modification to their site coming in April which will allow access to tracking but not account data.