I have considered this but what prevents the developer I hire to not just run away with the intellectual property ?
I think you underestimate the value of ideas.
Look lets be honest. Its going to take much more than a developer to just run away with your idea.
People are inherently lazy - and nobody cares about your idea more than you do. I gurantee that if you post your idea here, the responses you will get will shock you. Not because this forum has bad people (mostly), but because not everyone will beleive in just an idea.
And heres something even more surprising - there are already people out there who have the exact same idea as you. Heck there are even a few apps already out there that do the exact same thing as your brilliant idea.
Heres what matters:
EXECUTION
Hire a developer, have him / her sign an NDA and just start building it. When you take this approach, one of two things can happen:
1. You work closely with the developer to translate your vision and idea into sometyhing tangible, just like how its currently playing out in your head. You build this amazing product that millions will benefit from, and through that you will make the Forbes rich list soon enough. (Note this requires physically and mentally working your a$$ off, not just handing your idea to the developer and expecting it to magically be built in a week. You're going to have to work at a massive pace to make sure that your idea is still relevant while it is being built and make sure you are hands on with the developer that you hire so that dreams can become reality. Also, developers are not cheap. Especially the good ones. I assume that you have a million dolllar idea, so dont expect to pay peanuts to get it built.)
2. You continue worrying about your idea being stolen, and never start anything valuable to begin with. This is the easiest path to go down.
Ideas literally mean
nothing.
Yes, they can be VERY powerful if they are executed. But an idea is just that - something that runs around in your head without providing any value to the world.
Finally - if you do know of anyone in the business of buying ideas for a lump sum, let me know. I could retire tomorrow.