In App Game

I have a client who may be interested in developing an in app game . Like a treasure hunt scenario where people follow a map round a citry centre walking from attraction to attraction where a clickable info page and voucher will appear.

Is this type of thing possible ? I am looking for price guidelines and alternative ideasif this is not possible.

Any ideas/prices would be greatly appreciated and would lead to follow on work
if accepted.

The budget is a grey area for me so feel free to bid what you think