As a note to those of you considering Bluetooth, keep in mind that Bluetooth operates in the same 2.4GHz frequency range as traditional WiFi. While potentially harder for field staff to detect (as a WiFi scanner will not see it), if it is detected you will likely be told to stop using it.
I came across an interesting paper that describes, amongst other things, how WiFi and Bluetooth interact with each other:
http://www.hp.com/rnd/library/pdf/Wi...oexistance.pdf