Oooh, awesome. I'd had a bookmark to the "add fuel-up" page on my homescreen on my Android while I longed for an actual app. This isn't quite what I had in mind, but should still be an improvement, assuming I can remember the format.
I have all three of our cars under my account, so it'd be nice if I could also associate my wife's phone with her car without needing to put it under a separate account. Great feature though, especially nice for those of us without a smartphone/data plan.
I agree natefoo, and we're looking at ways to do that. We haven't decided how to handle multiple cars, but we're thinking about sending an SMS back if you have more than one car enabled. That would mean more SMS fees all around though, so we're still thinking about it.
If all works well, are there plans to expand this to other countries? I'm in Australia and would love to be able to add the details 'at the pump', rather than having to take notes and entering at a later date.