Camera lenses that let you see through clothing.

[Rydian]

http://www.kaya-optics.com/products/experiments.shtml

Of course, $130+ for just an entry-level lens might seem out there, but they have their uses, such as seeing through fog and tinted glass.

So. You get a camera and one of these as a surprise gift.
What do you do?

[Jipcy]

Perv.

Details about why this doesn't work for everything: http://www.dansdata.com/io002.htm#perv

[ReRuss]

that works with any cam... and a $20 bill...