Hundreds of thousands of UnitedHealthcare customers who participate in a health rewards program can now "walk off" the cost of an Apple Watch, essentially getting a $300 version of the device for free. The program could potentially encompass millions of new customers. Apple is increasingly in talks with insurers about getting the cost of its Apple Watch subsidized, as it moves more deeply into the health and wellness space. It held meetings in August of last year with another insurer, Aetna, to discuss ways to bring the device to its more than 20 million members. The integration with UnitedHealthcare, which is the largest U.S. health-care company, could mean a boost in sales of the Apple Watch as more people are able to buy it at an affordable price. UnitedHealthcare, which is part of UnitedHealth Group, covers around 50 million people. Since 2015, it has been investing in its program called "Motion," which provides rewards to those who walk more than 10,000 steps per day. Hundreds of thousands of people are enrolled in Motion through their employer, said a UnitedHealthcare spokesperson.

Employers can opt in by turning on the Motion program. Their workers can request an Apple Watch (up to a Series 3), if they don't have one already, and they pay taxes and shipping for a device. Once they receive their smartwatch, they get up to $4 per day toward the price of the watch by achieving certain activity milestones. Those who already have an Apple Watch, including the newer Series 4, can integrate it with the program to earn cash rewards for activity. Within six months, members can essentially earn the device for free and get extra rewards on top of via their health savings account. The Apple Watch Series 3 retails for less than $300, and the maximum amount offered through the program is $540 within a six-month time frame. The "FIT" program requirements laid out by UnitedHealth are as follows: Frequency: Complete 500 steps in seven minutes an hour apart, at least six times per day;

Intensity: Complete 3,000 steps in 30 minutes, at least once per day; and

Tenacity: Complete at least 10,000 steps per day. Those who don't complete enough goals to earn the cost of the watch within six months will be liable for a percentage of the cost of the device. Apple did not return a request for comment on the program.

A program for normal people, not just the "worried well"

Some health-care advocates fear that wearables are designed for the "worried well," the young and healthy population that can afford smartwatches and gym memberships. But this program is designed to be accessible to a broad population, and not just the super fit and healthy, a UnitedHealth spokesman told CNBC. "It's not marathon running," said Paul Sterling, the company's vice president of emerging products. "We start and stop at a basic of activity type, walking, which most of us can engage in and then we layer in a program structure." UnitedHealth is conducting studies of its own employees to determine whether it saves money if its members are using wearable devices, like the Apple Watch.

The company told CNBC that its internal analysis found that employers who joined its Motion program spent less per member during the first year than those without the program, with a year-to-year savings of $222. It also found that the highest participation rates were among people with chronic medical conditions. People with diabetes, it said, were 40 percent more likely to opt in to Motion than those who did not have a medical diagnosis. People with one or more serious medical conditions represent the highest cost burden for employers and the country at large. Chronic disease represents $126 billion in costs associated with lost productivity, the Centers for Disease Control and Prevention found. Employers face a cost of $245 billion in managing diabetes alone. Reducing these costs represents a huge opportunity for wearable computing, if companies across health and technology can figure out a way to bolster access and engagement and lower the cost of the devices. UnitedHealthcare is already integrated with other device makers, including Fitbit and Garmin. "Some [wearable devices] are expensive, quite frankly, and they provide meaningful benefit in terms of someone wanting to participate and engage in their health," said UnitedHealthcare's Sterling. "We recognize that and so we're trying to reduce the cost burden." Meanwhile, Apple has been looking to target an older, sicker demographic with its device. It introduced several features in recent months, including a fall detection service and a new sensor to detect a type of heart rhythm abnormality called atrial fibrillation, which is most common among seniors. It also announced a partnership with medical device maker Zimmer Biomet to study whether the smartwatch could help people recover more quickly from hip and knee replacement procedures, which are also more prevalent among its older users.