IPhone App for ToneFest Festival

I am looking into the possibility of having an iPhone app developed for a Festival I run each year in Dorset. I am looking for something along the same lines as the Camp Bestival Application (Download it for Free!). I would like to be able to add things to the application and make amendments myself, maybe make it amendable so I can keep using it year after year. I have my own server if that\'s how it is stored (like a website, I suppose). Anyway, let me know your thoughts and how long it would take to build, I am not interested in open ended quotes but would prefer a total figure based on your estimate of the time needed to develop it. Thanks in advance. Tony