I worked with Liangjie on the “Romantic Lighting Sensor” Lab for Sociable Objects Workshop. The basic challenge was to learn how to use XBee without Arduino as a remote sensing module.
We used paired Xbee Radios: A local Radio in API mode and a Remote Sensor Radio with a photo resistor (light sensor).

At first, we had some problem at the receiver side. It was pretty clear that the transmitter is working fine since while we were using just the xbee explorer board as receiver we could directly see the data coming from the serial channel. However we couldn’t get the code to work.
We ended up using a processing sketch to print out serial data from arduino.
Also, we learned that the resistor used to augment sensor output value to fit xbee’s 3.3v requirement has to be carefully handled, otherwise you do not use the full range of the sensor output.

Here are the documentation videos:
Xbee API Mode – simple remote xbee sensor

XBee API with feedback