Becoming The Godfather Of Smart Phone Apps
A good place to get ideas on phone apps is in social forums that target mobile users and developers. Many ideas as well as complaints are found in these forums. The complaints from users are great in terms of feedback as they will tell you what not to do with your app.
Developers will also tell you what you should avoid when creating
your app due to design complexity and programming tool restrictions.
Most of these forums are free and you only need to register to
participate in them.