A young guy once approached Isaac Asimov and said, "I have a great idea for a story. How about I give it to you, you write the story, and we'll share the profits."
"I've got a better idea," said Asimov. "I'll give you an idea and YOU write the story."
Mr Anonymous, ideas aren't really worth much. Your first step would be to create the app and THEN work out how to market it without getting ripped off.