This feels like spam, but anyway I actually have these. They don't work as advertised sadly. I put a temp sensor on the cup and the temperature curve didn't look any different than without the joulies.
I'm one of the original kickstarter contributor of coffee joulies. For me, it does work. Coffee came out of my keurig brewer are at drinkable temperate immediately. But I'm not sure if it can hold temperature longer. I guess I'm just using it a ice cubes without diluting the coffee and also not accidentally making it too cold