Assignment: develop a mobile application for a hybrid vehicle. Display the following information: amount of fuel, charge status, location, nearby gas/charging stations, etc. Easy. Do this in two weeks. Okay. And come up with a wildcard interaction of your choosing. ...Alright, sure.
Let's make this more about just keeping track of your car. Let's make this about the car keeping track of you. Not in a creepy way. You know, in a fun, friendly, checking-in kind of way.
Lots of ways to do that, but not much time, so lets keep it simple... What if the car analyzed your driving style, and assigned you a driving style/badge? You might brag on Facebook about how you're such a Roadtripper, or how you just won Hypermiler status. And this style would change and develop as you changed your driving style, keeping the user/device relationship fresh.