I haven't seen any one wear them, but really wasn't looking for it either.
And I had thought they were not effective. Can't remember where I heard or read that, but I just remember that they don't really do anything. I would bring it anyways though, just to try it. Stand somewhere and wait for a ton of mosquitoes to start chomping away at you, then turn on the device and see it if works
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Don't worry about looking stupid though. I've noticed in any area with tourists, there will always be someone who looks stupider then you ^