I recently bought a new Motorola Droid with Verizon. My son happened to get one too, and he suggested we sign up for Google latitude, which allows us to get see each others location from or phone or computer. That in itself was really cool. But you can also turn on history, and google will keep recent updates of your location. It's not clear for how long, but I have several days worth so far. Only I can see the history, it is not shared or made public.
You can export the history to a .kml file, and then you can create a map under mymaps in google maps and import that .kml file. Then, you get all of your history shown in a map suitable for sharing.
This past weekend I managed to get 2 1/2 days of riding in, we had spectacular weather here in Oregon, and Washington, and California. I did just under 900 miles.
So I got home and looked at my history, then did the .kml thing, and was really impressed with the result. Here's a link...
Kevin's Thanksgiving Run
The phone uses it's GPS or cell tower info depending on coverage etc. There are some obvious gaps where there was no coverage, but wherever there is you get a better track log than you do with SPOT. This is all 'free' with Verizon and Google, not sure about other carriers/phones. That is free in that it doesn't cost anything above the voice/data plan I have on my Droid.