Infrared filters like the Kaya Optics PF4 were available accidentally on Sony cameras some years ago, before being quickly taken off the market. Since then, voyeurs have developed an extensive after-market and DIY system for these types of filters that can "see" through clothes. Kaya's new filter allows you plug and play functionality into your existing recorders that use CCD (Charged Coupled Device).
The PF4 is probably either going to be banned pretty soon, or have strict restrictions placed on where and when you can use them. Until then, we look forward to seeing more mannequin nipples.