Ultrawideband Heralds Zippier Wireless Connections  SAN FRANCISCO (Reuters) - Think of it as Wi-Fi on steroids.  On its way to U.S. living rooms and maybe even automobiles is a  new type of high-speed wireless connection that promises  downloaded data rates of up to 1 gigabit per second -- roughly  18.5 times the speed of Wi-Fi -- to personal computers and  other devices.