Spoiler alert: the answer to this is almost always... no.
I've got a circuit that'll amplify. It stands up to some reasonably serious RFI tests on my workbench. I could install it, give my friend an 1/8" - to - RCA cable, and walk away. But would he use it?
Well, would *I* use it?
The intercom is a good three feet away from any counter or table. Which means a long wire dangling. So yes, I'd probably use it a couple of times, and then decide it's too much trouble. Gut the intercom, replace it with something more modern. And I'd like to avoid that eventuality; if the old thing works well, then it doesn't have to occupy a landfill.
What would make this thing more useful, then? That wire sure is a problem. So something wireless. Which, with audio, obviously means Bluetooth.
The "standard definition" Belkin SongStream bluetooth receiver is small. Like, a couple inches square, and an inch tall. It has an audio jack and a power jack. And no buttons. This is starting to sound like a Christmas present. I'm just not sure for whom...