Unless you disable the GPS, the phone is doing this (reporting its location to the net) anyway. And of course, all apps tell you right up front what they access. The only question is if you decide you want access to the data. Same for apps, I'm sure a subpoena could get that info, of course, I don't know who would care who knows what apps they have on a phone.
Saw a case out of Washington from 2007. Lady left home, disappeared without a trace. 8 days the hunt went on, cops were all over the husband, coverage on local news, etc. Just gone.
Finally, after severe legal wrangling, police were willing and able to get the last reported location data from her cell phone. Was less than 15 miles from home, on her normal route. Pulled a comprehensive search, found her car off into the vegetation off the side of the road. She was barely alive, but she was. Trapped in that car for 8 days. No food, no water. If her husband had has this tech, she would have been found that night.
