Xbee Network

I recently purchased two Xbee Modules ea. w/ a shield included directly from Liquidware: http://www.liquidware.com/shop/show/XBS/Arduino+XBee+Shield

My plan is to have a remote sensor w/ an Arduino+Xbee that can relay data to the "coordinator" (the Xbee with the destination address). The main issue is that they are not in direct line of sight. I was thinking of purchasing a third Xbee module that would receive and transmit the signal, and would act as an intermediary between the remote site and the computer.

The intermediary would obviously need its own individual power source, but would it require any additional hardware?, would it require another Arduino?