I'm guessing you're based in the US, maybe Canada? I like this idea, but dear god, please no one try this in the UK, or if you do, make sure it's expensive peanut butter (no Sunpat, people!)
I say this because I am an American import to the UK, and much to my derision, most peanut butter is a completely different animal over here. American PB generally has to consistency of margarine or butter spread. If you melt it, it melts and stays melted for a reasonable length of time. I think it must have more oil or something. Major UK brands, on the other hand, congeal almost immediately when you take them off the heat, and even "smooth" varieties are kind of... grainy. I imagine it would be a nightmare to get into your hair, let alone out. It's going to clump and stick like glue.
I might try this some time anyway though. I frequently request peanut butter to be sent in my care packages from back home, because I don't like the stuff here.