It turns out, once you go past '0 miles range' you don't get negative miles of range (which would be cute). You just get a somewhat impractical "Charge Now"... (oh, and the telemetry data shows 5% SOC at that point)
The data you can collect from the Mobile API. Search the forums for Rest API - or look at these two threads: Rest API and Telemetry Visualization
This picture was taken in my garage I crossed below 0 about half a mile from my house... it's an interesting feeling when the range drops below the distance remaining on the way home...
Yikes! I've only been as low as 8 or 9 miles remaining. As I understand it, it is bad for the battery to let it get too low.
