I have always used other plants and flowers as my repellent and it has worked well.
Although they did grab about 60% of the 150 transplants into a wood edge flower garden area this spring. Will allow the non-attractive-to-deer plants grow this year and transplant again next year.
At the bottom of this link is a listing a plants deer generally will not eat. I have many annual flowers mixed through my garden as well. Helps with pollination by attracting bees and keeps the deer from sniffing around.
http://usagardener.com/disease_pests...the_garden.php
The spray type repellents seem to have a good effect and I like the idea of a motion activated system. Would be funny to see the kids activate that as well when they walk by.