Hello - good question. You are on the right track and it is important to make sure you have the legal rights to use this content before you incorporate it into your app. Emailing the content owner is a good start and you don't have to provide anything more than a summary of your app along with your request. This will help reduce the risk of them "copying" your idea.
Patents are a different thing altogether and would not protect your "idea". Once you have developed your app, copyright laws will provide you with a measure of protection.
If the content is important to include in your app you will need to ensure you obtain appropriate rights to use it. A lawyer can assist you with your initial request and can help make sure you have broad rights to use the content if the owner agrees to license it to you. Good luck!