Whistles have for quite some time played important roles in many areas of human activity including:-
1) Refereeing (e.g. football, darts)
2) Survival (e.g. Attracting attention of passers by after your 747 has safely ditched in the middle of the Atlantic)
3) Saving lives (e.g. Swimming pool
4) Communication (Sheep dogs, train guards, wolves and kettles)
That said, there is the underlying assumption that the operator is able to deliver the required amount of air at the necessary speed and time to achieve the desired affect.
A referee may for example be asthmatic, on the phone, sneezing or indeed all three at the crucial moment.
The mouth-free whistle would look just like a normal whistle but have a cartridge of compressed gas and would be operated by pressing a button. A referee could of course still put it in his mouth to achieve the desired dramatic effect, if that was important. The cartridge would be replaced in a similar way to inkjet printers cartridges or batteries.
.and have a remaining life indicator to warn them when power or puff was running low.
Another advantage is that while pressing the button, the user would still be free to perform another task including shout at someone, make a phone call or have an asthma attack. If youre floating in the middle of the Atlantic with two punctured lungs, you could potentially be in big trouble if you werent armed with a Whistle-o-Matic.