I use the Delorme Inreach satellite transmitter device:
http://www.llbean.com/llb/shop/76340?pr ... google_plaYou get three canned messages that you compose beforehand and can have automatically sent to three parties plus the SOS button which automatically notifies SAR. My routine is goes something like this: #1 OK, made it; #2 Delayed, but OK; #3 OK, but having mechanical problems--(KEY: this one also goes out to my competent flying buddy who agreed to act as dispatcher and organize other local competent flyers to assist); and finally #4 for life-threatening condition, the SOS button which notifies SAR.
The nice thing is that you receive confirmation that messages are sent (my understanding was SPOT does not have this feature). A mapped location of your position is sent on a really detailed topo map which converts to aerial image at high magnification. Unit is around $250 and service plan is approx 10 bucks a month.