[EvanK]

Very interesting idea. Though, this seems like it would be much better suited as an Android/iOS/etc app to live on the phone itself.

[swah]

Perhaps it still makes sense not to assume everyone on a car has internet access?

[yanda]

The reason I went with a phone number is that phone calls generally play well with cars (in-car bluetooth headsets, etc...) whereas audio for apps usually has a harder time connecting to in-car devices.