I love the implementation. You should branch out and do the same with other cryptocurrencies. Such as litecoin and dogecoin.

You should also program an investment maximum while the site is gaining popularity as to not screw up the BTCBTCBTC wheel.

For example, if they send 1btc while the site is still new, send them back .99 with an attached message saying they sent too much, a penalty fee has been charged and credited to the investors.