Heatermeals are frequently marketed towards truckers & other long-distance drivers. I've seen displays in the local truck stop. They're functionally equivalent to an MRE, in that you have an entree & a chemical way to heat it, requiring only water (in this case, salt water, but they provide it in the package) & time.

I've tried a few over the years, & I've still got one in my desk. They're not bad, as convenient emergency food, especially. The spaghetti tomato sauce was very acidic--Tums or other antacid is a must!

David