Android App for Medical Reps

I need an android app to be used by medical reps (sales people working for pharmaceutical companies that visit doctors for marketing and making product presentations). Also a server app + web interface needs to be done to host central data. Features required: 1) User account creation and management 2) Location detection 3) Chat room for medical reps which is to be filtered based on parameters, e.g. Area and medical rep speciality (e.g. cardiac, psychiatric, etc) 4) Space for advertising on android app. Ads targeting can be customized from admin account on server app based on parameters. These are the main features. Use case scenarios will be given for chosen bidder. These may and probably will be customized. I'm looking for someone who actually gets a feel for what I want, and maybe even engage in suggesting new features. Preference will be given for such bidders. I'm looking for implementation in Java technology both for android app and server app. But also open for other technology choices. This should be really easy for someone who knows what's he's doing. I'm expecting bids in the low range. Happy bidding!