Designer Sophie Horton's Mana squash training aid aims to prepare the player against muscle imbalance and shoulder injuries by developing muscle strength in the player's arms. Its mechanism is inspired by 'ghosing' drills which give the player vocal instruction during practice.
Mana clips onto the racket, with weights that can be adjusted according to the desired level of play, and gives vocal instruction during practice.
So instead of having a coach shout at you, you can now have your own racket do that. Al least you can control to volume!