Made for Timcel's set of protest whistles on Thingiverse, the integral loop will let you conveniently hang one of them from a lanyard or cord near a spot that is common during an emergency (near the first aid kit, for example).  Simple snap-in / snap-out operation keeps debris and rain out of the the mouthpiece and clips into the whistle holes on the sides.  STL and 3mf files included.  Mine was made for indoors, so used Bambu basic PLA in red & white, use PETG or better for outdoor use.  Partner to my other safety whistle cover.