I looked up suggested serving temperatures for coffee and got 71 to 85c, room temperature is usually 22 to 25c. So that means my dT would be, at best, 46 to 64 c, which on that plot gives me 1.3V@0.65@ to 1.5V@0.9A. That should be enough to light atleast one red LED, though they usually like about 2V, most that I see say 1.8-2.2, and I have to take into account that the heat sink will probably warm up quickly. So I'm not really sure if it would work. I guess I could use 2 of them, but were already looking at $20 or so here.