DASH Express GPS is an upcoming product that utilizes crowds moving as traffic sensors. The approach is very similar to what is done in TNT, with the difference that the comsumer/user of navigation devices acts also a FCD sensor, i.e., each unit is basically a two-way pager, it records the traffic you experience and shares it with others!

The stats to have such a system work are the same as in our case, >2000 vehicles for major (pop >1.5M) is a must in terms of penetration to have decent traffic assessment!

This GIZMODO article tries to shed more light on the specific approach.