Researchers have studied the benefits of an implantable medical device designed to alert users about a potential heart attack through a combination of vibrations, audible tones, and visual warnings.

I’m on a new kick: silent wake-ups. The vibration setting on the SleepTracker watch I reviewed has turned out to be a far less agitating way to start the day than waking up to a blaring alarm clock.

Heidi Cruz got a surprise last spring when she checked her smoke alarm. When she pressed the button, it beeped like it should, but her 6-year-old daughter, Adriana, didn’t react to the noise. “It ...