Wired has a good story about ZigBee,"a specification for building large networks of low-power radio transmitters". Expect consumer products by the end of the year. Because of the low-power consumption, batteries will run for years. Applications include home-monitoring systems and checking up on the elderly.
"Kill the Wabbit, Kill the Wabbit, Kill the Wabbit!"
-- Looney Tunes, "What's Opera Doc?" (1957, Chuck Jones)