Most Japanese homes have these small tamagoyaki fry pans for rolled up eggs on the go. If you know anything about tamagoyaki - you will understand why you need this. If you don't you might like to read up on it.
Check out our Just Bento cookbook for recipes/tips - because they use it there for sure. In fact you can see a tamagoyaki on the cover in the bento on Just Bento 2.