Self heater

So, they make self heating cans of food and beverages for camping or lazy people or people obsessed with novelty.

I kind of like it as an application for camping. But the problem is that one can of self heating food is heavier than a dehydrated bag of somthing. So here's what I propose. A reusable (shocking!) bag that can selft heat. I've seen similar technology for hand warmers. So basically you through the dehydrated food in the bag with some water, activate it, wait a few minutes, and enjoy.

The heating agent would need to be well sealed in the liner and it would need to be able to cool and down and reheat somehow. But this is way possible.

Again, I ask the scienticts to get on this effing one.