This is a little hard to answer because it is so vague. It depends on the area, the market and the strength of innovation. I know that The App Guy has a terrific podcast at http://www.theappguy.co/ and is also trying to organize a community for App developers to sell their ideas. Let me know if I can be of further assistance to discuss patentability in terms of its value to getting a sale or license. What ever you do, don't spend money filing a full patent, just a provisional. Good luck.