How Does a Device Know When You’ve Fallen?

After the sensors detect the motion and hard impact of a fall, the device typically triggers an alarm that’s loud enough for others in an area to hear. Many devices can also dial 911 and selected personal contacts for help using Wi-Fi, cellular signals or even landline connections.

Plus, devices embed GPS coordinates. These can be relayed to emergency contacts to pinpoint your location and find you sooner.

Your iPhone can help prevent a fall

If your iPhone is running iOS 15, which debuted in fall 2021, it can use data on your walking speed, step length, double support time (what Apple calls the proportion of time that both feet are touching the ground when you walk) and walking asymmetry (the percentage of time that your steps with one foot are faster or slower than the other foot’s) to determine your walking steadiness.

You’ll have to give Apple’s Health app permission to gather the data — you don’t have to share it outside of your phone. And after the app records at least seven days of information, it will assess your stability while walking as “OK,” “Low” or “Very Low.”

The assessment, which is updated every seven days, can’t predict your fall risk, say, today. But if your stability is rated as low or very low, your fall risk within the next 12 months is elevated.

The Health app suggests exercises to improve your mobility. But you also can share this information with your doctor to create a long-term plan for increasing your stability.

At the moment, Android phones, a little more than 2 in 5 of the smartphones in the U.S., don’t have an equivalent feature, but the same sensor is within them. Just about all smartphones and tablets in use today have triaxial accelerometers, according to information from Gary Weiss, head of the Wireless Sensor Data Mining Lab at Fordham University in the Bronx, New York, who does research into ways these sensors’ data can be used.

Most people take this sensor for granted. It’s what allows a phone to adjust its screen display when you change its orientation from vertical to horizontal.

Linda Dono contributed to this story.