Happily, through experience, I can report that the affect on battery life is not noticeable.
So the solution is simple: allow Safari, and thus Latitude, to run in the background (even while the i Phone is locked and in your pocket.) You might have already guessed that forcing the i Phone into enabling this functionality requires a jailbroken i Phone.
If all goes well you will end up installing the extension and restarting your springboard.
You'll see a new app, Backgrounder, on your home screen that contains some documentation but go ahead and launch Latitude right away (open Safari and visit google.com/latitude).
In case we need to define precise location, we had to switch between network and GPS location providers (as GPS doesn’t work indoors) 2.