It's a brave new wireless world, yet most portable-audio hounds are still tangled up in headphone cords. Soon, though, you'll have lots of wireless stereo headphones to choose from. The technology isn't brand new, but until recently it was too bulky and expensive to shove into the tiny, splurge-worthy gadgets we love. Expect to see three flavors of wireless earmuffs-Bluetooth, Wi-Fi and magnetic induction [see sidebar below]-rolling out between now and early next year.