I went to a stock dog trial yesterday, and it dawned on me as the handlers sent piercing loud whistles across acres of land to the dogs, the whistles might be another idea for an emergency whistle. The metal and Corian ones are high in price, but I picked up a couple of plastic ones to try at $2 each. They are small, light, and flat, making them conducive to EDC and PSKs.

Sorry I couldn't get a picture of one to copy over to this post, but the link below is the vendor I bought them from. The website is down while they are away, but will be back up when they get back from the trials.

http://www.bordercollicsanonymous.com/home.html

http://www.isds.org.uk/acatalog/WHISTLES___LANYARDS.html