I have one of the first versions. The OK button sends out a check-in message. It actually sends out five times in case the sat's not easy to access. The system ignores after getting a ''good" report, so the final OK message gets sent out only once. The help button can be setup to either send a help message out, or summon road service. Your choice when setting up the service. The 911 button will bring out the rescue teams.
So... the OK and help buttons are set up in your SPOT account. You set up your canned message. My OK is ''This is a check in message and/or position report only." The help button is ''The Jeep/boat/bike is disabled, and I/we are stuck here. Help!" Of course, on a planned trip to the woods or canyons of Moab etc. you set up your list of SMS's and emails that get sent out. Both the SMS's and emails have internet links that lead to maps for where you are. That way, the people at home can call out tow trucks or whatever. They will have a set of GPS coordinates to give whomever is heading out to help out.
There are warnings about the 911 button. They tell you that you better darned well need it before using it. If the sheriff or rescue team gets dispatched because you ''wanted to see if it really works'' it could lead to jail time or paying big $$$ for wasted rescue personnel time. If a chopper flies out to where you are for nothing, you don't want THAT bill! And once the 911 message is sent, it's like a bullet - there's no recalling it. Everyone on your SMS/email list will also get your 911, and the dispatch center will be calling them for more info. (You set up emergency numbers and contact info in your account)
An optional feature (in the service, at a little extra cost) is the breadcrumb trail mode. (At least what I call it) The SPOT will send reports every 5 minutes. Otherwise, you do them manually. The AA lithium batteries will send about 1,900 OK's before going. I tend to do them at forks in a road or trail and another a little after, or some other ''milestone'' as I go.
The cool thing about the dispatch center, is they know exactly where you are due to the GPS in the SPOT. If you're on the side of a highway, they'll assume it's a medical problem or wreck, and dispatch accordingly. If you're in the middle of Canyon Lands nat'l park, they'll assume its a fall from a cliff or the like. If you're off shore, they'll assume a sinking boat and send the coast guard. Whatever, you will get help soon.