X-bee have Serial interface this means you will able to comunicate with them using serial protocol, a Pic or other controller is a must,
first you have to define the X-bee address, address are used to identify them in a RF network, let’s say device ‘AA’ is the sender (where the sensor will transmit) and ‘BB’ is the receptor where the data is going to.
next: all you have to do is use the X bee as if your device were wired!, in other words comm are transparent when X bee are well configured, just send a char ‘A’ and the other end you got tha same ‘A’.