The deal could also improve sales for the Apple Watch, which is the top-selling product in the wearable tracker market. 4. Aetna was the first U.S. insurer to partner with Apple to subsidize the Apple Watch's cost, according to a Bloomberg report from last year. As part of the 2016 deal, Aetna offers the Apple Watch to its 50,000 employees under its corporate wellness program. Apple and Aetna declined CNBC's request for comment. More articles on health IT: NIST finalizes 'NICE Framework' for cybersecurity workforce development Microsoft unveils Coco blockchain framework AHRQ awards Regenstrief Institute $1.7M to study patient matching