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, and to his health insurer.

Schmidt, an information technology specialist from Carrollton, Texas, was shocked. “I had no idea they were sending my information across the wire.”