Rabbit Semiconductor is part of Digi International, as is MaxStream; so it is not surprising that the new $299 ZigBee/802.15.4 Application Kit employs MaxStream's XBee ZigBee module. The module is linked to the RabbitCore module via a serial link (see Figure).
The 2.4-GHz XBee module ($19) is a self contained ZigBee node with its own processor and protocol stack. It has an open-air range of 100 m at a speed of 250 kbits/s. It supports ZigBee as well as 802.15.4, which ZigBee is based on.
The kit contains three modules and three battery-powered carrier boards. The RabbitCore module also has a carrier board. The module has Ethernet support, 512 kbytes of flash memory, 256 kbytes of SRAM, a 1-Mbyte serial flash chip, and 33 GPIO lines.
Rabbit Semiconductor's approach has significant advantages for developers. Check out my interview with the ZigBee alliance ("Zigbee Surprise 2: The Response") to determine what level of participation in the ZigBee Alliance is necessary. The module approach is the least expensive approach, especially if you don't plan on using the ZigBee logo on your product.
The module approach is also the fastest and easiest way to get started with ZigBee, since the protocol stack is contained within the module that handles all communication chores. It also eliminates this protocol overhead from the host processor.