Works. Do you have to but do not necessarily have.

First, it should be mentioned that the "egg cooker" his service provides as described.

Compared to a conventional egg cooker but neither time nor energy costs are saved.
A conventional egg cooker also works indeed with a very small amount of water is directly heated and has besides the advantage that you can - depending on the model - can cook about 6 eggs at a time, and the measuring cup has graduations for linen / medium and large eggs ,

With this model you have all the cooking time, depending on size and wattage, identify and record yourself.
And then, of course, find the records again.

So, a nice Gimik. But no must-have.