Millions of sleep apnea patients rely on CPAP breathing machines to get a good night’s rest. Health insurers use a variety of tactics, including surveillance, to make patients bear the costs. Experts say it’s part of the insurance industry playbook. Last March, Tony Schmidt discovered something unsettling about the machine that helps him breathe at night. Without his knowledge, it was spying on him. From his bedside, the device was tracking when he was using it and sending the information not just to his doctor, but to the maker of the machine, to the medical supply company that provided it...