You'd probably want to rethink things a bit, given that the empeg UI was built around four buttons and a spinner, while the Tesla has a mammoth touchscreen. That said, the first people to write apps for the Tesla will inevitably be the various big music services (Pandora, etc.). Given how many Teslas are floating around Google, I wouldn't be surprised to see ports of the many different Google apps with automotive relevance (Music, Maps/Navigation, and inevitably Google+, if for no other reason than the head of G+ owns a Tesla).
The big question for me is whether Tesla goes the Android route (well supported by ARM) or the web app route (growing in popularity, and making it pretty damn easy to port existing apps). I'll bet they go for web apps, if they do 3rd-party apps at all. I expect, with security concerns and whatnot, that they might just put off apps in their entirety, or at the least only allow them from "approved" vendors.