This is the phone locking mechanism I’ve designed for my First Person View (FPV) racing goggle university project. On the left is the initial test piece and on the right the final test piece. A clockwise twist will lock the phone into position and when you want to release it, press the button and rotate it anti-clockwise. Simples! To use that is, designing it all to fit into a headset and accommodate several phone sizes… not so simples.