So, not to interrupt a good curmudgeon fest, but I bout my mom an Ember mug for Christmas two years ago, and she loves it.
Her style of drinking hot beverage at work involves nursing one for an hour or two, and her tea was always getting cold, which necessitated microwaving, then waiting for it to cool back to optimum drinking temp, then having it be too cool and repeating. Now it's the right temp from 10 min after steeping (she prefers tea) to the very end. If she takes her cup to a meeting, or another office to talk, the battery keeps it warm till she comes back. She says it's her favorite office mug by far.
Personally, I drink my coffee before it gets cold and just make more, but some people, I guess, caffeinate slower.
The Ember Mug also tops James Hoffman's list of ways to reheat/keep coffee warm without losing the flavor.
But I also have wifi light bulbs, so there's that.