The fundamentals are that I will have one 3G connected arduino with xbee centred in the field with 4 digital sensors each connected to their own xbee. Every unit will be solar powered. The sensors will be going high for various lengths of time but I am only interested if they go high and back to low within a short period, say 500ms to 2000ms. When this happens I want the central arduino to log it. I don't need to know which sensor has triggered, the data is treated as one and the same.
What I need advice on is:
a) should I be using beacon or non-economic(w/coordinator) mode?
b) should I have an arduino at each sensor use IO line passing to send a pulse if the sensing period is within my criteria, or should I ditch the arduino at each sensor point, using only xbees with IO line passing, and do the criteria matching with the central arduino?