Waze is a social mobile application providing free turn-by-turn navigation based on the live conditions of the road.
100% powered by users, the more you drive, the better it gets. Join the community of drivers in your area today!
The UK is still in "building stage" which means drivers are currently "building" the GPS network. After this stage, the data will become reliable as more and more users submit data, and others can benefit by using this data. The system also appears to remember traffic flows to help you avoid unnecessary delays to your journey.
Seems like a good idea to me.