I was using one, let's say TRYING to use one, last year with a couple of Uway NT50B cams. Unfortunately, the NT50Bs were either not working, working intermittently, or only working occasionally. This made it very difficult to evaluate the black-flash extender. Honestly, I had trouble in even being able to tell when it was working, or not. But it appeared, the battery life was relatively short compared to most of the newer cams.
I like the idea of being able to use this black-flash extender as a means of converting a white-flash (or a red flash) cam into a true black-flash unit. Main draw-back I currently have with the black-flash unit itself is its large "foot-print", especially since it's in addition to that of the cam.
Am currently experimenting with that Uway black-flash extender coupled with a Leaf River cam. Will share my results when available, but do not expect battery life on the flash-extender to be as great as the cam's battery life. Will depend in large part as to how many times the unit is triggered at night, as well as the flash-extender's settings. I left it on it's highest output setting.