Patenting is the worst thing you can do. Don't you read all the patent BS going around lately? Also, spending money on a patent won't be enough, you'll also need to spent money enforcing it, and you won't make any friends by being a litigator.
All you can do is provide the best product you can come up with and hope for the best. If someone makes something similar but better, well, you'll just have to work harder. Or drop the whole thing.
But as others have said, you'll have this problem on *all* platforms. A practical example, when Nero released their burning app for Linux, my thought was "This is kinda cool, but why would I pay for Nero, when there's K3B and other apps that to the job, but are open source and free?"
The trick is to provide something others don't have. In the case of NeroLinux it's familiarity for ex-Windows folks or dual-booters. In your case it could be more features, better graphics, easier to navigate interface, regularly provided additional content... something in that direction.