We just invested in a motion-triggered sprayer that attaches to a garden hose. I switched it on overnight to deter a vicious tom that was spraying our patio furniture daily. For a few days I would come down in the morning and see it had been activated, with no sign of him having left his calling card. Then it appears he gave up. Probably still visits the garden but not near patio. Only problem? You have to find a way of switching it on/off without getting a soaking!