There are a few controllers that have a logging feature built in. The Alltrax "AXE" lineup allows datalogging by connecting a computer (laptop in a car) using a COM cable to the controller.
I have the 48V version of that controller on my electric motorcycle, but don't have an appropriate computer to bungie-cord to the cycle!
I have thought that data-logging, combined with GPS info would be really interesting. That way, you could learn how much power is used going up big hills, in higher speed zones, etc.
We joked about this for Toms Neon conversion, which will have a very nice custom battery management system. Seriously though, I think he might be able to integrate GPS with controller data-logging.