Hi,
I've read and understanding what you need, but need to confirm which storage online service should you use for your application? Dropbox or Google Drive, because each service has its own API.
We are a software company, concentrate on Mobile Application, Facebook Application, Web Application, Windows Application.
In Mobile Application, certainly we focus on Android Application Programming, both hybrid code (HTML5,CSS3,jQueryMobile,PhoneGap) or native code (Java). I have an application in Google Play as well, named A-Football, if you want to check please search and download it to use. And one project for client in oDesk, named Prestige RealEstate (in both iTunes AppStore and Google Play).
My proposal is below:
1. Cost: $200
2. Time: 15 working days (w/o Sat, Sun)
3. Milestone: (M1) 20% upfront and get app for testing, (M2) 80% next and get app (after bug fix) and source.
4. Guarantee: 3 months after acceptance.
Thank you and good luck with your app.