I don't think its a question of good or bad idea. If you want your idea to be realised but don't know how to develop, you kind of only have one option.
There are plenty of developers out there who will be able to create something for you. The question is what are you willing to pay for the work? It will only be interesting for developers if they either get paid or if they see a potential in your idea and are willing to do the work for a % of the sales.
There are quite a few radio apps out there already that most likely will be adapted for the iPad. To compete with them may not be of interest to a developer.
Only one way to find out though. Approach some developers and ask.