A snip at 120 $
http://www.hammacher.com/publish/72698.asp?&source=NEWS3106&cm_ven=WC&cm_cat=20060803_News31&cm_pla=INQ&cm_ite=r2_d2
I'd buy one if I had a pet.
It'd be hilarious to see a cat hiss & spit at it.
I'd doubt whether a cat would take much notice, once it is clear that the thing doesn't like cat food. A Scotch terrier, however would be a completely different proposition.