Whilst there are plenty of 'low tech' solutions to stop...err...conception, there is now a preventative prophylactic apropos for an EcoGeek in the works. The remote control, implanted device will allow users to 'press pause' on their sperm. (although it doesn't mention whether a 'rewind' function is in the works). The device has been developed by Australian scientists, and could herald a new dawn of even more convenient contraception for men, which has the potential to keep population growth under control more effectively.
A surgeon inserts a silicon chip into the vas deferens. The fob sends out RF waves, just like the key to your car. The silicon chip converts the RF into acoustic waves, which in turn induce movement in the material, allowing it to expand and seal the tube. Sending another pulse from the key fob lets the material contract allowing sperm to pass.However, to avoid 'cross talk' with say... your cordless phone, WiFi or bluetooth.... ultrahigh frequencies are used, combined with sophisticated coding, to make sure that no mistakes can occur.
All they need to do now, is integrate a button to turn off the lights so you can save electricity.