On the $ side, I've worked on a couple lifestyle apps - there is money there but they have to be really huge (lucky for me they did in fact become huge). On th

On the $ side, I've worked on a couple lifestyle apps - there is money there but they have to be really huge (lucky for me they did in fact become huge). On the marketing side, the key for the stuff I work on is that the app is about 10% of the project, the rest is distribution. So I'd think about apps that can spread via twitter, facebook, email, etc, and then build a simple app around that. Make the app simple, and really focus on the "marketing" side of things. "Marketing" in quotes because it is really still development though.