There are many mobile app builders out there, but often they aren't great at creating custom native apps.

Contracting a developer to build a custom app can be pretty expensive, up to 200k in some cases. I know of companies who have created a joint venture to share profits, etc., but this is when the company getting the app built already has a massive following.

An idea alone may not be much of a bargaining chip, but, add some funding to it, and some hard work, and we've seen the basement start-ups that have followed and become wildly successful.

It might be worthwhile to search for "mobile app developer" groups on LinkedIn, Facebook etc. to pose the question to see what kind of feedback you get.