The Off clip on mosqiito repellent devices work much better than I expected. So long as it not real windy, and you are not moving around a whole lot, they do a great job.
I tested them out one year an Flamingo camp ground in the Everglades N.P. The mosqiitos were horrible. I went out with the clip on turned off. I was immediately covered with mosquitos. I turned it on, and they all vanished, After half an hour, I tried turning it off. Inside of 5 minuted, I was covered with mosquitos again.
Joel