Android/I-Phone API app - open to bidding

I need to develope a combination sheduling app...whereby the consumer can just shedule an appointment at a particular time and most of the time from their place of business...and I need the consumer to be able to open app and see if one of our techs are in their highrise office building, five start hotel, convention center, or are just within 1/16th of a mile from where they are; I will begin with maybe 10 technicians but will grow to at least 100 technicians. I will have a developing consumer base of 1 to 1,000 and if all goes well it should grow to over 4,000 possible consumers/customers/client base. I will be beta testing of this "startup" January or February 2016...let me know what you think...thank you....Michael Bendick in San Francisco