Close to four years after the original Apple Watch launched, the smartwatch market is looking less like the smartphone market for Apple (AAPL) - Get Report and more like the MP3 player market did during the iPod's heyday.

Research firm IDC's latest smartwatch sales estimates drive this home. In the seasonally big fourth quarter, IDC thinks 10.4 million Apple Watches were sold, up from eight million a year earlier. With the firm also estimating that smartwatches accounted for 34.3% of a total wearables market of 59.3 million units -- this figure also includes fitness trackers and Bluetooth headphones -- its numbers imply the Apple Watch accounted for slightly over half of all Q4 smartwatch sales.

For comparison, IDC thinks the iPhone accounted for just 18.2% of Q4 smartphone unit sales, and research firm Strategy Analytics has estimated the iPad accounted for 26.5% of Q4 tablet unit sales.

As is the case in the smartphone and tablet markets, Apple's smartwatch revenue share is undoubtedly well above its unit share, given the difference between its average selling price (ASP) and those of major rivals. Whereas the Apple Watch Series 4 starts at $399 and the older Apple Watch Series 3 starts at $279, many smartwatches from rivals such as Huawei, Xiaomi and Fitbit (FIT) - Get Report have starting prices below $200. Fitbit's just-launched Versa Lite smartwatch starts at $159.

Moreover, outside of devices supporting Alphabet/Google's (GOOGL) - Get Report Wear OS, third-party app support for rival watches is often fairly limited. And in many cases, the interfaces and visuals of rival products have more in common with traditional mechanical and digital watches than something like Apple's watchOS (see Samsung's Gear S3 and Xiaomi's Mi Bip for some notable examples).

In addition to a strong app ecosystem for its watchOS operating system, Apple's investments in advanced health features have clearly helped the Apple Watch's cause; the Series 4 added an electrocardiogram (EKG) function, as well as the ability to detect falls and irregular heart rhythms. The company's chip and hardware engineering strengths, which have allowed it to pack a relatively powerful processor and 4G connectivity, while maintaining acceptable form factors and battery lives, also hasn't hurt.

And as Rolex and Omega would gladly tell you, image and branding are pretty important in the watch market. Here, Apple has a clear advantage over most smartwatch rivals.

Though the smartwatch market hasn't lived up to some of the initial hype surrounding it, Apple has created a pretty lucrative smartwatch franchise that continues seeing healthy growth. And judging by both industry stats and anecdotal evidence, this franchise, like the iPod before it, maintains a pretty enviable competitive position.

Apple and Google are holdings in Jim Cramer'sAction Alerts PLUS Charitable Trust Portfolio. Want to be alerted before Cramer buys or sells AAPL or GOOGL? Learn more now.

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