Spiky Flip Flops
My wife bought me some of those spiky flip flops which are supposed to massage the soles of your feet. They are fantastic. The coolest thing is that after you've been wearing and walking around in them for a while, if you take them off then the carpet feels like you're walking on air.
I wonder if you could use the same technique for other things. Perhaps if you have a headache you could wear an incredibly uncomfortable hat for ten minutes so that when you take it off you find that the pain of the headache has been completely removed.
What do you think, should I start making a prototype?