Comments about Coghlan's Coghlan's Four-Function Whistle for Kids:
Yellow makes it easy to find. Plastic is durable & thermometer is accurate & easy to read. Magnifying glass is cool, but most importantly the whistle is loud. I don't know how loud these things should be, but it's piercing.
However, the compass was stuck when I received it. After banging it around for about 5 minutes the compass set in place properly & was functional.