Is there a good method for transmitting a syncronization pulse wirelessly to multiple devices?
The NNTP protocol can sync your R-pi's wall-clock times together and periodically correct for any drift. So at least at the system level there is a solution.
However,the R-pi CSI-2 connector specifically lacks any provision for hardware sync or master clock, so that kind of kneecaps the whole scheme. Without frame sync, over time each camera's framing will drift, ruining the frame correlation you need to properly sense distance.
If your camera has its own sync pins available you could possibly use another approach (e.g., infrared) to provide a master sync reference.