Just this month, the insurance company United Healthcare began partnering with employers to offer free Apple Watches to those who hit certain fitness goals. Insurers might also offer benefits to residents whose homes prove their fitness or brand loyalty—and punish those who don’t. Health insurers could use data from the kitchen as a proxy for eating habits, and adjust their rates accordingly. Landlords could use occupancy sensors to see who comes and goes, or watch for photo evidence of pets. Life-insurance companies could penalize smokers caught on camera. Online and in person, consumers are often asked to weigh privacy against convenience and personalization: A kickback on utilities or insurance payments may thumb the scales in Google’s favor.