Magnets are beginning to gain the attention of home-electronics manufacturers and government agencies as an alternative to Bluetooth and other short-range wireless techniques. This week, Troy, Mich.-based manufacturer Fonegear began selling cordless cell phone headsets that use the properties of a magnetic field. The headsets, which cost between $60 and $80 each, are the first wave of mass-market electronic devices that use a new generation of magnet-powered wireless technology.