Ooh yes, that looks like a good start. Presumably that's measuring the mug warming up rather than down (hence, presumably, your comment about needing to tweak it a bit), but it looks like basically the right thing.

Now all it needs is the extra mechanism for detecting an empty mug – preferably without dangling something grubby in the drink. I feel there ought to be something clever along those lines: some sort of micro-seismic detector, perhaps, that wobbles the mug slightly and then 'listens' for ripples bouncing back from the far side to see if there's still liquid in there.

That's a very clever idea! Wobblemug :)

Actually, eTea has a timer for brewing; the temperature-checking part of the gadget is (as I remember it) what starts off the timer. You may need to tweak it more than a bit.

I recommend dorkbot meets.

Ah, yes, that would make sense. (It was difficult to get proper information since the main eTea website is empty apart from a link to a video, and I wasn't even conveniently able to watch the video with sound :-)

Is this equivalent to something that pings the mug and checks what the pitch of the ping is?