Think about it this way: Good app developers have tons of options including high cash employment, higher cash contracting, and lots of great startup options that are funded AND offer equity. Your idea could be the greatest thing ever but unless you bring something relevant to the table you aren't likely to get a good developer. What is "something relevant"? UI Design experience, server side technical expertise (if relevant), product management experience, or previous business success.
If you have the last one you probably aren't asking this question. If you have any track record of success, I'd be hitting up your family and friends for enough capital to get an alpha version out to test your idea. That way you'll feel comfortable that your "unique" idea is not stolen. Last point I'd make is that your idea is probably being worked on by at least 2 or 3 other teams right now. Your real challenge is to execute on that idea (idea=1%, execution 99%).