I'm a HUGE fan of SPOT but only if used with www.spotwalla.com
The issue with findmespot.com (the mfg's site) is that your trips go away in 30 days - not good if on a 44 day trip like I bought mine for!!
I've used mine from Key West to Prudhoe Bay and back to Tampa:
A trip to MD and back:
And even a silly short trip to AL and back (Barber Vintage Days):
My wife likes it so she knows where I am, but I DO have to agree that if it is mounted onteh bike it could be useless to signal for help in a crash. I mounted mine on my bike, but risked not being able to signal for help if I crashed.
I especially like the spotwalla integration and ability to post links to photos on spotwalla, even if I never HAVE linked a lot of mine (started but got busy)...