I have a very similar product in development, but security concerns have made me cautious to release it so early. I notice you are not even using a self-signed SSL cert on your site. Can you describe any existing security measures and plans for security? With the recent Bitcoin 'disappearances' I think this issue is paramount.

Also, how do you plan to mitigate exchange pricing and support, considering Coinbase seems overloaded with orders. Or are you dealing strictly in Bitcoin for now?