I found this site:
that has some information about using such features on mobile devices with Apple's Safari and Mozilla's Firefox Mobile web browsers. I don't know all the browsers available on modern cell phones or the capabilities of each. I also found this list:
If any of you have any guidance, advice, or whatever, or are willing to help me test a script that I write since I do not have a GPS-enabled phone, I would appreciate it. Something like this would be a cool feature I would like to add to my site. Right now, I'm walking in the dark.