I would like to know is there any software that will make my Macbook Pro's iSight camera work as biometric authentication by capturing my face? Any free or paid software are welcome (preferably free). I have tried to google it but I found only some forums with posts from 2004 and nothing helpful.
KeyLemon looks like what you want: http://www.keylemon.com/product/
It has a free version, but I don't believe it will replace the login screen.
I'm not aware of any software that will allow you to do that.
I would comment on the KeyLemon suggestion, but I don't have enough rep!
I do not think this will replace the standard OS X login screen. It looks like it will add another, working like a screensaver, to restrict access to your machine once you have logged on.