Hi Guys - I just noticed this thread. Thanks for the kudos.
Me and kids (mostly my now-16-year-old Ben) put this together after I took delivery of my Model S in Dec 2012 and went on a road trip to Vegas (Barstow supercharger). It was obvious that the on-board tools really weren't that useful and that Nav, Energy and a well-calibrated model needed to be integrated in the car. My older son is in college studying CS and was a real physics buff, so we did some physics 101 and realized we could predict energy for a given route pretty well (if you get speed, temp, etc right). For what it's worth, though, Elon seems to be selling cars OK without this! Anyway, we're proud to have thousands of users planning routes every week and believe our accuracy is improving. Some things you might want to check out:
* version 1.1 unreleased has some algorithm tweaks to handle altitude and cold better:
EVTripPlanner
* check out the interactive map of where folks are planning routes:
Where The Teslas Go
We tried integrating with weather info (wind more than temperature), but it is so variable by time and position that I think it would make errors worse - that's why we just do the "weather sensitivity table".
We could add other EVs, but would need some decent data to do our initial curve fits to.
(and, in case you didn't notice, Ben takes donations to his college fund on the site!)