When an alarm in one part of the house senses smoke or carbon monoxide, it sets off its own 85-decibel siren and every other alarm's too, communicating over a wireless 915-megahertz radio network. The alarms also announce the location of the fire or CO leak. $80 per alarm
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.