Many sports now require participants to wear mouthguards.
This includes team sports such as rugby.
The problem is that it’s hard for eg a pack leader to give instructions during play, when his mouth is obstructed by a lump of silicone rubber. Calling the required line-out throw, for example, can easily be misheard.
Today’s invention therefore consists of a gumshield with a loudspeaker, a battery and a processor inserted.
By biting down on the shield n times, instruction n can be barked out, with perfect diction. There could easily be 20 or so such standard orders and more elaborate patterns, eg involving tongue position, could increase the repertoire.
Players might choose to use the simulated voice of Ironman or one of the Transformers. In International matches, the accent of your opposition could be used to confuse them.