The XBee series of 2.4GHz communication modules take the the 802.15.4 stack (the core of Zigbee) and lays a very useful serial command set on top of it, making them very popular with a huge user community. If you want to take any sort of serial data and beam it "out there" wirelessly, this is the critter for you! Did you know they  also talk point-to-point or in a multi-network mode? Swarmbots - woo-woo!

This particular model is the "XBee 802.15.4" (formerly Series 1) part XB24-ACI-001, and features:

• 1 mW chip antenna (great for tight spaces)
• 1 mW output (but the chip antenna designation kinda gives that away already, huh?)
• 250kbps communication speed
• 3.3V @ 50mA power consumption
• 90 meter (300 ft) range (in ideal circumstances, but really, these do have good range)
• 6 10-bit ADC input pins
• 8 digital I/O pins
• 128-bit encryption
• Industrial temperature rating (-40° C to 85° C), so feel free to use it in your hot-tub in Iceland.
• FCC certified for USA, Canada, Australia, & Europe. No worries about men in antenna-laden vans driving up to your house with a "you've been naughty" look on their faces.

• [Documentation]: XBee Manual
• [Schematic]: XBee Mechanical Outline
• [Data Sheet]: XBee Datasheet