Augmented Reality basic app for Iphone with server management routine

We are looking for a basic augmented reality app for Iphone and Ipads. The main functionality we require for the app is to be position and location aware. The app should have map overlayed on portion of the screen. The app should be able to receive location information of other app users and display it on the overlayed map as dots or whatever suits the device. The app hence requires a server that receives individual location data from app users and send the location data to selected users. This means the app would require registration of users devices,details and consent for the user to be able to be part of the network of users. So lets say we are in London oxford street, we want the app to be able to show on camera that we at oxford street and that the location of other app users in relation to us.