Birth Control for Men
Recently I've read an article that warned men who are currently trying to get their wives/girlfriends pregnant to spend too much time in car seats, especially when they have heating. The simple reason is that the increased heat in that sensitive area can reduce fertility.
I thought if this is something to consider for folks who want kids, it might also be interesting for those who don't want them. So I did some more research, and found out that in the 80s, there was a group in Switzerland that called themselves the "testicle bathers" (seriously) and who experimented with heat as a birth control method. They discovered that, by bathing the testicles in 45 degree warm water (Celsius) for up to two hours daily over the course of three weeks, they were able to induce a period of complete infertility for an amazing six weeks! (And yes, this was actually checked scientifically, not just learning by doing.)
Now this sounds like an April's fools joke, but apparently it's not. The whole idea got forgotten due to various reasons, obviously the process was ridiculous and tedious, but also as HIV/AIDS came up contraception needed to meet other requirements. Still I find the whole story quite fascinating as a proof of concept, and I actually believe that picking up on the idea again with modern technologies could be very worthwhile. I'm envisioning piezoelectric underwear that would provide the necessary heating energy by itself and protect the wearer of unwanted pregnacies.
The advantages are obvious as this method would work locally without forcing one of the partners to induce a major change to the entire body system (as the birth control pill does). Advantage or not, the sociological implications, provided that the method is reliable and gives men true control over the reproduction process, could be huge as well.