Write an iPhone application

I would like to get a popper quote for an app that will let me add and share events on a Google Map. Example : One user goes /drives by the sea and sees something interesting. He can then taps one button on the app to ADD an event at the current GPS location with a short description. (20-30 letters or so). The event will be marked with a circle / dot on the map and other app users will be able to see it on the map and also get an audible alert on their device. Other users can then visit the spot and confirm or negate the event. Other app users will be able to see how many have confirmed the event. Main features of the APP should be : - Add event - Confirm / invalidate existing events - Event should expire automatically of no user can confirm the event within 30min/1h - If there are more invalidation than confirmations the event should be delete. - Users will get a notofocation / warning when they are close to the GPS location (radius of warning to be defined) - APP will give notofocations even with the screen closed / locked. - Language should be configurable in 1-3 languages and I will provide the translation. - Each event should have a small ICON on the map. If the app needs a back-end server to hold the data I can provide backend with MySQL database or PHP or whatever else needed. I would like to have a quotation for this kind of app and I may or may not choose to go on with the app , depending on the price.