The open-source GPS-enabled app takes full advantage of the crowdsourcing idea. It's as much a step above Google Maps as Google Maps is above my idea of putting radars and cellphone modules all over the place. It has access to an online map database that can plot routes just as a dash-mounted GPS unit does. Everyone who uses Waze contributes traffic information that can be used by everyone else. This data is used to determine routes -- and to get real-time route updates while driving. If traffic is building up ahead, Waze will let you know and suggest an alternate route. If you pass an accident, a speed trap, or dense fog, you can touch the screen and send the report back to Waze to be annotated on everyone's map.
Interestingly, it's not just the traffic data that is crowdsourced. The client app that runs on the phone is open-source, and anyone who is registered with Waze can edit the maps themselves. You can edit the maps in your Web browser or directly from your phone, just by selecting the "pave" function and driving a new road. I recently made my first edit by deleting a segment of road that used to exist until it was bought by the Open Space people, who put up a gate.
Waze isn't perfect. I live out in the boonies, and the app sometimes suggests an exceedingly scenic route to get to work or to my kids' school. I don't mind driving aimlessly through the mountains, but sometimes I need to get to places on time. Most drivers, myself included, already know how to get where they're going, so a flaky routing algorithm isn't that much of a problem. Alerts on speed traps, hazards, and traffic speed are much more valuable and work very well. Also, it's just plain cool to look at the GPS tracks left behind by thousands of users as they go about their day.
Waze is free for the iPhone, Android, or Windows mobile platforms. Take a look, and try out the map editor, as well. Happy driving.