Some motion-sensitive pendants can detect a fall and summon help. (Gary Cameron/Reuters)

You’ve probably seen the ads on TV and in magazines — especially that iconic “I’ve fallen, and I can’t get up” commercial that, yes, is still running. The makers of medical-alert systems promise swift help in the event that you have a medical emergency while home alone, whether it’s a fall or a heart attack, stroke or seizure. The ads are reaching a receptive audience: Sales of med-alert services are growing and are expected to continue doing so as the baby boom generation ages.

Should you consider buying one, for either yourself or an aging parent who spends time alone? Here’s a quick guide on what the systems offer and what to look for when you shop:

Make the most of technology

Medical-alert systems were introduced in the 1970s as simple push-button devices worn around the neck. They summoned help by signaling a base station connected to a home phone line that would alert a call-center operator. Today’s systems are still wearable, but you can also mount help buttons throughout the home and install devices that allow for two-way voice communication with call centers. Some companies offer motion-sensitive pendants that can detect a fall and automatically place a call for help.

Who needs one? Most buyers purchase a system for an aging parent who lives alone and might have difficulty getting help quickly. That person might be at a heightened risk for falls because of poor eyesight or memory changes, says Barbara Resnick, a professor of nursing at the University of Maryland and a past president of the American Geriatrics Society. The systems can also be useful in a non-emergency situation where a person doesn’t need an ambulance but does need help. The call center will alert a preselected relative or friend who can assist.

What to look for

If you’re in the market for a medical alert system (expect to pay around $30 a month for the basic service), the experts consulted by Consumer Reports said the best ones meet all or most of the following criteria:

● It works for a user’s specific disability. For example, a stroke survivor may need a device he or she can activate with one hand.

● It offers a choice of a wristband and/or neck pendant. Cords worn around the neck can pose a strangulation risk; wristbands might irritate people with skin conditions.

● It includes help buttons that can be wall-mounted near the floor in multiple rooms in case the user falls and isn’t wearing the pendant.

● It offers multiple choices for whom to contact if the user needs help, from emergency services to a friend or relative who lives nearby.

● It has a battery backup in case of a power failure.

● The base station can be contacted from anywhere on the user’s property — even in the yard or at the mailbox.

● The company has its own monitoring center, located in the United States, and employs its own trained emergency operators (rather than contracting that function out).

● The monitoring center has been certified by Underwriters Laboratories (UL), a nonprofit safety and consulting company.

Copyright 2014. Consumers Union of United States Inc.

For further guidance, go to www.ConsumerReports.org/Health, where more detailed information, including CR’s ratings of prescription drugs, treatments, hospitals and healthy-living products, is available to subscribers.