This has been discussed to death, but I'd like to add an approach that I haven't seen brought up before.

An HTML5 app/site can be a great MVP. You can build and iterate quickly and even launch it first as a mobile web site. Once you're happy with everything, you can use PhoneGap to turn it into apps. And later you can always build platform-specific native apps. It won't be the perfect experience at all stages, but it can be a more appropriate process for smaller teams. Plus, you can reach a large audience very quickly.