This is basically a cross between a SpectrAlert and an EST Genesis, where I put my EST Genesis (case being in the video posted above, the remote strobe) on the SpectrAlert “Classic” mounting bracket. More info is in the description of the video posted above.
Edwards / EST does have a trim plate that fits around the Genesis for situations where it would need to be attached to a double-gang or a 4x4 backbox, btw.
Unlike some bad retrofit installations, these two alarms seem to compliment each other, since the Genesis fits into the SpectrAlert strobe area nicely (almost).