I've used oDesk in the past and they have some really great tools to ensure you can track what the contractors are doing when they bill you for hours. e.g. They

I've used oDesk in the past and they have some really great tools to ensure you can track what the contractors are doing when they bill you for hours. e.g. They will take a screenshot at random times when the contractor says they are working on your project so you can see that they were actually working on your project and not just sitting around doing nothing. The key to finding good contractors is to start out by breaking down your project into smaller pieces and giving the contractor one small independent piece to implement for a fixed price. If they deliver on time and quality work commission them to finish your project on an hourly basis. For javascript and android development I would recommend an excellent developer that I've worked with before. Oscar De Dios Rodriguez