Could this unit be worked into a scanner to keep the audio level constant?
The alert tones are loud as **** and the dispatchers sometimes whisper,
so hearing the call can be difficult.

Scott... good question. The answer is yes... but with some conditions.
My feeling is that you were looking to disconnect the scanners
speaker... and insert such a device between that connection and the
speaker. I hope that is a correct assumption. The problem is that the
VoiceMax module has been designed to drive an impedance of around 1K
or higher. So in order to use VoiceMax in that application... you
would have to add perhaps a small audio amplifier (op-amp or single
transistor) connected right after VoiceMax to drive your lower
impedance speaker load. Hope that helps.

Actually, I would tap into the volume control by cutting traces.
I intend to work with the line-level signals.