Last year, I was camping at the paintball field for a weekend long game in my ENO doublenest. It was the worst it could be as far as heat and humidity.. zero air movement, an unyielding hot sticky feeling and being that I carpooled, no escape. I did not sleep at all that night.. not a wink and that did not bode well for me the next day during the game. As a backpacker, I would have simply accepted fate but car camping can afford you luxuries for those situations that might not be ideal. I THOUGHT I had given myself one of those luxuries, as I had my massive Kelty Noah's Tarp 16x16 set up with FEET of space all around me, set up for any breeze to make it's way with no chance of getting rained on.. you can imagine how my tent yielding teammates fared.
So now I hunt for a battery operated fan that can hang from a ridgeline. I believe that ANY air movement would have gotten me at least a little sleep that night, positioning myself in less of a diagonal lay and creating a chute with the excess hammock material to trap the air movement so it can flow over the whole length of body. I saw this guy at Wallyworld but D batteries are expensive and this takes 8... thought it is nice that it can plug into the wall should I need it for home use.
Perhaps others have fans that they have used in the past, maybe even small enough to put in a backpack setup? It would take something crazy effective for it's size for me to make space in my pack for such a thing but hey.. maybe there's something out there?