Radios: XBees are made by Digi International and there’s plenty of kinds to choose from. We recommend starting out with the 802.15.4 XBee with a chip antenna. This will adequately cover a small indoor space, or a larger outdoor one (up to 100 meters). If you need more range, there’s the 802.15.4 XBee Pro which can cover over a mile outdoors. However better range comes at a price. The Pro version is slightly larger, somewhat more expensive and will cut your battery life to a quarter of what it would be with the standard XBee.
Antennas: If you’re planning to integrate your circuit into clothing, it’s probably best to use a radio with a chip antenna (as opposed to wire). The chip antenna has a somewhat shorter range, but it’ll stand up better to wear and tear.
XBee models: There are a wide variety of radios in the XBee series. Maybe a bewildering variety. For wearables projects, we recommend the 802.15.4 XBee or for more advanced projects that need mesh routing, the proprietary XBee Digimesh when it becomes available. XBee ZB ZigBee Pro radios are better suited for stationary networks, because the routers and coordinators that make up the network need constant power and benefit from a stable physical layout. The ZNet 2.5 has been deprecated, so that’s not recommended at all.
Look for more information on configuring XBees in upcoming tutorials for making your own Wireless Wearables.