The most effective counter argument is that ISP want to be allowed to slow these same services down.

"Well, you bought an ADT security system, and they are not a Preferred Security Service for Time Warner, so even though you pay for 40Mb internet, we can only allocate 4Kb to ADT."

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.

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.

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.