Waze: Crowd-sourced real-time (lagged) traffic information

Waze is a mobile smart-phone application that lets you see real-time traffic information from other Waze users, and share it. Basically, it uses your smart-phone as a probe. It also lets you update the network (of course if the network is still incomplete, real-time traffic data is almost assuredly sparse). This really depends on critical mass, as I described in this paper:

And lagged information may in some instances be worse than no (or historical average) information.