For the most part an idea is a very small part of creating a successful app. Sure, you have to have a good idea to begin with, but many great ideas have failed in this competitive landscape. Regarding patents, that's the last thing you should be worried about. App creators and companies do not get patents. Patents are very expensive and can take a couple years to get, which doesn't work with apps at all.
You will not be able to sell your app idea, either. Everyone has ideas. It's the ones that follow through and build out the idea into a viable business plan that have a chance for success.
Hope this insight helps you. I see way too many people throw their money away by not understanding how the app ecosystem works.