Since the 1970s, medical alert systems have been making it safer for older Americans to live independently. About a third of seniors aged 65 and older fall every year, and half of those 85 and older fall every year. A medical alert system can mean the difference between life and death.

"Emergency Response Technologies are important, because falls are the number one cause of death due to injury" in people over age 75, Andrew Carle, executive-in-residence at the Program in Senior Housing Administration at George Mason University, told Live Science. He said that falls "are also the number one cause of hospitalization due to injury for this age group."

Introduced in the 1970s, the first systems were simple devices worn around the neck that called for help by pushing a button that was connected to the home phone and went to a call center. Newer gadgets still use devices attached to chains, but can also contain motion-sensing technology that can detect when the wearer falls. It issues an automatic alert to the company's emergency dispatcher who checks in with the wearer and sends emergency help if needed.

Newer devices are more subtle than earlier ones, cutting down on a patient feeling stigmatized, says Carle, and some use newer wireless technology that allows them to work everywhere.

According to Live Science, the three best medical alert systems are:

1. Medical Guardian. The user can move 1,300 feet in any direction while staying protected, and the base unit's battery life lasts up to 32 hours. The company offers many options that include in-home models as well as GPS versions that operate away from home. Fall-detection technology is also available. There are no activation or cancellation charges and no long-term contracts are required. A 24-hour help line is available, and the staff keeps a list of your family and friends who can be notified in case of an emergency.

2. LifeFone. LifeFone Personal Response Service's waterproof pendants have a 360-degree coverage with a 480-foot range as well as a model with a 1,000 foot range featuring a base console with a 32-hour battery life. Smoke and carbon monoxide monitoring is also offered as well as pendants that can detect falls, and the company offers cards users can carry in their wallets to give doctors and other medical personnel worldwide their health history. There's no activation fee, and contracts, which are available in increments as short as one month, can be cancelled at any time.

3. Bay Alarm Medical. Customers using the Bay Alarm Medical Alert System waterproof pendant can move 1,000 feet in any direction. The system usually works even if the user is outside. Smoke and carbon monoxide monitoring are also available. The in-home system works via landline or cellular. Customers may opt-in for the 24/7 Automatic Fall Detection Alert System or mobile GPS Medical Alert System for expanded protection. There are no long-term contracts, and service is offered in 170 languages. The website offers live chat support.

Consumer Reports suggests that consumers look for medical alert systems with the following features:

• Offers both wristband and/or neck pendants
• Has a battery backup in case the power fails
• Base station can be contacted from anywhere on your property
• Monitoring center is certified by Underwriters Laboratories
• In addition to contacting emergency services, offers multiple choices for help, such as relatives and friends
• Offers help buttons mounted in different rooms in case there's a fall when the user isn't wearing the pendant
• Monitoring system located in the United States with its own trained operators