Those little cyclones don't get hot at all.
I'm sure you could add a switch. In of those like on a lamp cord that you rotate. Would cost a bit more. Obviously up to big blue.
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Joe is correct. They give off no heat at all.
As far as Amber placement, its just like an antenna, you want them high, not on your bumper. Dust, mud, dirt, snow will cover bumper placed Ambers in no time.
As far as a On/Off button. You can certainly splice in a switch, I am just making these simple and cost effective. The vast majority of the cost in the the Cyclones which are $29 each.