Hi asgm, thanks for your quick reply.
So in the interests of not voiding any warrenty,I could use something like the Zigbee STH-03ZB, connect it to my xBee WIFI module, leaving the explorer board the only other hardware required? Apologies for my knowledge, just trying to get this clear in my head before I proceed.
No, that is not using a Xbee ZB module but using some other persons Zigbee enabled product. You would be better off just getting a GROVE LTH sensor and an XBee GROVE board. Then connect your XBee WIFI module on the Grove board and the sensors to the board.