You have received a lot of good information.
My only contribution is to consider the times you ride where there in not any cell-phone connection. I have been in many areas where it was nonexistent; which would cause the obvious problem.
I use the following:
http://www.findmespot.com/en/index.php?cid=101
This specific unit works on satellites; which increase your chances of having a signal. I have used it in mountains and remotes areas with consistent results.
It does provide cookie-crumbs; however it does so fairly often... every few minutes... so tracking is as accurate as one would want in my opinion.
If you stop, the cookies will cluster in that location until departure; giving the person tracking you an indication of problems if you do not move on soon, or do not report a reason for an exceptionally long or unexpected stop.
In addition, there is a "Help/SOS" button that contacts authorities in the event you need help. I wear mine on my person so it goes where I go in the event of an accident.
There is also a pre-set message (you create) that is sent via email to the person tracking you so they know you have arrived to a destination. There is a second message you can choose in the event you need help, but it is not an emergency.
I bought mine because of a motorcyclists who crashed and was found days later in a deep ditch. He survived, however, if he had this unit he could have pushed the SOS button revealing his exact GPS location via satellites -- and saved himself days in a ditch (not to mention the pain, suffering, and bug-bites that covered his body).
The unit requires an annual subscription to the service; but to me it is not that much.
Good luck in your search...
