I received the Munchkin safety rubber ducky as a baby shower gift. Sometimes with a new baby it is difficult to tell whether their bath water is too warm. This rubber ducky has a blue disk on the bottom that has the word HOT on it. The word HOT turns white if the water is too warm.
I used this a few times when my first child was very small. After a while I could tell whether the water was too warm and no longer needed it for its safety function. It is, however, nice to have just in case.
Even if you do not use the safety feature anymore, the duck is nice and big and watertight so it doesn't fill with water and leak everywhere. I like that. But, it is a little more expensive than regular rubber duckies and chances are it won't get much use as a safety ducky.
Munchkin also offers duckies that have different occupations, so if a fire ducky doesn't suit you (my husband is a voluneer firefighter, so it is fitting for our house) then there will likely be another one for you.