I had to remove a few pacemaker batteries when I worked at a crematory. We threw them in bin in the processing room and until they ran out of juice, they’d beep like crazy periodically. They’re made like that so that while the person is alive, they’ll know when it’s disconnected.

It was drilled into our heads that the crematory retort would be RUINED if one of those things went in with the person.

edit: typo and more context.