I backed the kickstarter project for coffee joulies, and my pack arrived yesterday. Initial reports have not been good. I used three of them this morning, in my normal Contigo West stainless mug, in lieu of the usual ice cube I normally drop in there to make it drinkable right away. The temperature change is definitely slight but noticeable. I use milk and no sugar. If I add no ice cube, it’s undrinkably hot for about 20 minutes. With an ice cube, it’s drinkable right away, and stays what I would still call hot for about an hour. With the joulies, it was still almost too hot to drink after a few minutes, but not quite too hot. Nearly three hours later, it’s still about at the temperature it’s usually at about a half an hour in.
More experimentation is warranted, but I think this is a thumbs up.