Check out CCC's article on fooling finger print scanners, im not gonna post the link, but its an interesting read :-)

Ive used a retina scanner before and my eye was a good 1 - 2inchs from the actual ccd and you didnt need to actually touch anything, it was pretty call tricking it also and hearing the robot voice of the woman telling me i wasnt a valid user, after doing it 10+ times she never got cross! such a bonus on a human!

i2c