Given enough Bluetooth distance information, stored in a central place, the location can pretty much be calculated exactly. No GPS is needed. More accurately in densely populated areas. The algorithm is called distance geometry. The distances don't even need to be exact. So be very careful with statements about privacy concerning location.

The original story is at http://www.rug.nl/cit/hpcv/nieuws/touchscreen1 and there are plenty of details in the text belonging to the youtube at http://www.youtube.com/watch?v=AlWFtF06RFo&hd=1.
In the original story there is no claim for the world largest, but perhaps it is the worlds largest curved screen. How knows.
It is not used for teaching math, but if a professor comes along to give it a try he/she is welcome to do so. It is used by students studying interaction methods as the best method for interaction will change with a big screen. It is also used for teaching students about Geographic Information Systems. For that application the resolution kind of matters.
Note that we only added touch detection to an existing 3D screen and we did so for very little money ( $2500).