I don't know how good this is but seems cheap enough
Egg-Per'fect Colour Changing Egg Timer changes colour as the eggs cook.
Sits in the saucepan with the eggs.
Soft and hard boiled eggs cooked perfectly every time!
Graduated scales show when eggs are soft, medium or hard by sensing heat instead of time. The sensor accounts for number of eggs, the amount of water, even the altitude at which the eggs are being cooked.