I put my phone on airplane mode. I used to try to study for hours straight but toward the end I was burning out and just set a timer on my phone for 90 min and I would take a quick break and then reset the timer.
Also developer of Mastermind watch had to develop a new product. They claim to be 100% compliant. Color zones might give a suspicious proctor pause. I'll stick with the Casio at half the price. https://answerwatch.com/