Yes, there’s a (Google) app for that:
In conjunction with the launch of the Android-powered Motorola Droid smartphone, Google on Wednesday announced the beta release of a turn-by-turn GPS navigation application with voice guidance for mobile users.
Google Maps Navigation is a free app that will essentially turn Android 2.0 phones into a GPS navigation device. Information is gathered from the Internet – specifically Google Maps – rather than satellite data used by most GPS devices.
On my first-gen, GPS-free iPhone, Google Maps could do a reasonable job of pinpointing my location by triangulating off of local cell phone towers. Out here in the boonies where towers are scarce, that didn’t work so well. But when trying to find my way back to the highway from downtown Denver, it worked great.
And I imagine that Google Maps uses a lot less battery juice than GPS does.
Lousy for hiking, but great for the city — not bad for free.