After prating around on eBay i found something called a IR filter.
I've goggled and it seems only to be used by people who want to see through nylon clothing on woman to see the 'fun bits'.

Are there any other uses for them other than voyeur viewing ?

There may be some useful stuff for you on this page :

http://en.wikipedia.org/wiki/Infrared_photography

Do you have a link to the ebay page ?

They are good for lots of things better than seeing through clothes!
IR photography can look amazing with the right subject and setting. For some examples, seehttp://flickr.com/search/?q=infrared&w=all

There may be some useful stuff for you on this page :

http://en.wikipedia.org/wiki/Infrared_photography

Do you have a link to the ebay page ?

http://cgi.ebay.co.uk/INFRARED-IR-FILTER-Sony-xray-1000nm-Hi8-TRV-65-TRV65_W0QQitemZ180261833877QQihZ008QQcategoryZ1507 5QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

that is one of the pages, i have noticed the see through clothing thing is only for Sony camcorders with night vision built in.
There is a more graphic one on eBay that shows nipple through t-shirt shot but i'll leave that out.

It's not that i was being dirty , just wondered what the use was for other than the eBay adverts.