No - it's nothing sophisticated. It's just a solid plastic sort of hemispherical (hemi-eggspheral?) object that has some kind of temperature sensitive colour-changing layer inside. So the pink bit that says 'Hard, Medium, Soft' will slowly turn white from the edge to the middle as its temperature increases and as it crosses the bands then you know when your egg has reached how you want it. It doesn't clip anywhere, you just put it in the water next to your eggs.
It costs like $2 and it has that cute little chick on it, so there's no excuse for everybody not to have one!
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