to be completely honest, this is dumb. how close are you standing next to people that they can see your phone? and as john pointed out, just turn away lol. when people need something like this for a computer it's because it's stationary and always near onlookers. with a phone, it seems like a circumstance where privacy is an issue would be much much less. unless you're cheating on your girl or something and you dont want her to see your texts ha. i remember hearing about these before and at first i was interested, but then i realized how pointless it is for a mobile device. save the money or buy something more useful... like beer!
however, here's one from dcmugen (reputable company):
http://cgi.ebay.com/1-PRIVACY-Screen...item518e3cc85f