Google Map API

http://code.google.com/apis/maps/documentation/
http://particletree.com/gmaps/workoutTracker.php

To write your own google map app, you need apply a API key. Then, just use the javascript object to use those function.

You can also test some function on the address bar:

javascript:void(prompt('',gApplication.getMap().getCenter()));

This will return the accurate Longitude / Latitude.

http://XXX.googlepages.com/gmap.html