I came across a recommendation for this product in an article about running, and it sounded like a good idea. It's also not very expensive, which is appealing.
http://www.kiienterprises.com/
http://www.kiienterprises.com/dazer/index.html
The Dazer II
"Using the latest ultrasonic technology, the DAZER II produces a discomforting but not harmful high powered sound, audible to dogs but not to humans. Help stop the approach of unwanted dogs at up to 20 feet. Also a useful aid in training dogs. Made of lightweight high impact plastic, the DAZER II features a belt clip and low battery indicator, includes a long life 9 volt ENERGIZER® battery and is MADE IN USA."
Have any of you heard of this product and/or used it? If so, what do you think?