We use the Thermal Cooker from Thermos. Works really well for dishes that have a lot of liquid - think soups, stews. I'm still experimenting with what works well and what doesn't. The instructions say to bring contents to a boil for a few minutes and then place the pot inside the thermos.
Pricey, but we paid for it with the $$$ we got from selling a complete set of all-clad when we emptied the house. And I like to use the pot for other cooking
too because we are only two people, it's a small-ish, heavy bottom with tall sides. If we need to brown a couple chicken thighs it's a great way to help contain the grease splatters.
We did our first overnight passage
a couple weeks ago. I started a beef stew a couple days ahead, froze it, then thawed it the morning before we left. Just before leaving at 3 pm I re-heated to boiling, put it the pot in the thermal container and we had hot stew at around 8 that evening.
I also use it regularly to make yogurt.