A colleague of mine at Great Oak HS, Reuben Villar, found this wicked cool app at Absorb Learning.
Click below to access the free online version of the app, by Adrian Watt.

We incorporated this app in our latest lesson, Tubicopter (sample page here). It intensely challenges student understanding of graphing by directly contrasting the physical flight path of the helicopter and abstract shape of the graph of the relationship between time and the helicopters altitude. Toy with it and leave your comments here.