Possibly some sort of telesurgery device? It'd never be acceptable to have something like this in the home, though, really, for all sorts of reasons, so it's not a good excuse. Network prioritisation or no network prioritisation, telesurgery over your cable connection is not a good idea.

There are remote monitoring services that track the status of various medical devices geared towards detecting anomalies in things like heart rate or heart rhythm. The ones that I've heard about use the cell network to report updates back to the monitoring company.

It depends how crappy the Internet becomes. If ISPs are allowed to deliberately crappify the Internet [1] then medical devices may need either need a fast lane or a separate network. And then ISPs will argue that the fast lane is the cheaper option.

[1] If you think this is hyperbole, consult the Comcast Backdoor Santa leaks.