Okay, link all individual recording devices beforehand, have each device determine and apply a correction factor so that all clocks are calibrated to the same external standard within a certain degree of accuracy over a given period of time before drift causes them to fall out of tolerance. You then have a known time-period during which the clocks will remain in close enough sync without communication with each other. Each recorder stores it's own time-stamped BWAV files locally, so you can start and stop recording on each device at any time within that period, yet all files will remain in sync and fall into the appropriate place when imported into editing software.
No wireless communication required.
If pushing a physical button on each device and staggered start/stop times are a bummer, use some sort of 'wireless' signal for transport control - click the tuned dog-clicker, flash the IR beacon, pull up the smartphone app, key the CB radio transmitter or whatever.. that aspect of the system is no longer required, but simply a convenience.