Lisa,
I have one of these in my garden cos I got p1ssed off with my neighbour's pets killing the birds and cr@pping in my verges.
Works a treat and saves me having to get a gun licence and a 30mm Browning off one of those there Boeing Superfortresses.
http://www.conceptresearch.co.uk/index.htm Go to the products page and see 'Ca****ch'.
Harmless and a great deterrent.