I still have one!
It's broken because it was designed by crazy people.
(The battery is required, the battery failed in such a way that it leaked and ate everything on the battery charger/temperature board, so uh, I have to find a replacement controller board and then put a new battery on it and I have to admit I just haven't been motivated enough to try to find a non-destroyed board from a tiny production run that's like 30 years old now.)