Protruding a mere ½ inch from the ceiling, the Silhouette smoke alarm from Kidde delivers innovative technology in a stylish package. The device uses an ionization sensor that detects changes in voltage caused by small particles (such as those from smoke) entering the sensing chamber. It also contains a rechargeable lithium battery—sealed inside the unit—that recharges automatically from the home's electrical system. A matching carbon monoxide detector will be available this fall. Kidde, 800.880.6788;