The SPOT is simple to use. You log into an online account. You then type what messages you want sent with your OK, Message, and Help buttons. The message can be anything you want for those three buttons. Sometimes I program "I have a bull down here, come and help me get him out" into my Message button, and have it sent to my buddy. You cannot type your own message for the 911 button.
When you push the OK, Message, or Help button it sends your corresponding preprogrammed message to any ten emails and ten phone numbers (text only) you put into your online profile. The emails contain your message, your Lat/Long and a link to your location on Google Maps. Text has only your message and Lat/Long. The 911 button has the SPOT dispatcher contact local search and rescue.
Hope that helps.