It appears that iPhones and 3G iPads are keeping a running log of GPS locations in a hidden file on the phone.  The log contains every location the phone has been to; it’s essentially a running GPS loge of everywhere you go.  When the phone synchronizes to the computer (and is backed up), the hidden file is copied to your computer.

Alasdair Allan and Pete Warden have created an application that will decode and plot these locations on a map – if you are using OSX.  more on this can be found on their iPhone Tracker site.

I’ll wait for the Windows version 🙂