This works as good as 'dog' and doesn't eat dog food :) The Ultrasonic "CatStop" cat repeller works pretty much like other electronic pest repellers by using ultrasonic waves. The device sends a 2-second ultrasonic alarm that can cover 330 square feet, which only the cats can hear and is quite unpleasant for them.  The cat soon associates the area with this unpleasant experience and avoids the area in the future. It works pretty well outdoors and is weatherproof, so you can use it to protect your vegetable garden or flowerbeds. 

This ultra-high tech cat repeller uses a 9V battery, which is claimed to last about 9 months. So, if you really really hate cats this is what you need to get; completely non-violent. Available for US $49 from here.