The Bringrr makes it nearly impossible to drive off without your phone. The four-inch dongle connects to your car’s accessory port or cigarette lighter, and if you turn the ignition with your Bluetooth-enabled phone more than six feet away, an alarm sounds. $35; bringrr.com
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.