When you get home you know your significant other is going to want sex again.
So you need a legitimate excuse, pop a coin into the public head ache device and walk away with a migraine intense enough to prevent your sexual performance.
You would be able to select the intensity of the headache you choose. Also the machine would dispense aspirin for an extra fee.
It could function in a variety of ways. Maybe its a bell that you stick your head inside of and then a hammer hits it. Or it could me a microwave type device that fried your brain a little. Or maybe its video and audio based, flashing images and irritating sounds until you are on the verge of a seizure.-- vfrackis, Apr 14 2009 Not tonight, Josephine.Seriously, though, I was under the impression that you did not need the headache - simply express the contrivance that you HAVE a headache.-- gnomethang, Apr 14 2009 And did any one get their leg over the following night [21 Quest]?-- gnomethang, Apr 14 2009 Proof positive, then!-- gnomethang, Apr 14 2009 [vfrackis] come on over to my house. I'll give ya a headache for free. No charge.-- blissmiss, Apr 14 2009 A Public Head Archer might be expected to lead his brigade of bow-and-arrow armed men through the streets of London in some kind of ceremonial function, perhaps performing a ritualised Cupidic action at the end of The Mall.-- zen_tom, Apr 15 2009 A Public Head Acre, might be of some advantage to those that like dogging.-- 4whom, Apr 15 2009 random, halfbakery