Whistles and compasses built in to caps are good for boaters and meet the regulations of Ministry of Natural Resources. The whistles will not stop working if they get wet, as they do not contain a bean.
Whistles are good for children in case they get lost.
The compasses are great for the hikers in your family and are always there with you and your repellent.
All whistle caps have a hole for a carabiner so they can be easily attached to your back pack.