Samsung

Apple Watch was the leading smartwatch in the second quarter, with an estimated 4 million shipped worldwide, for a market share of more than 75 percent, according to Strategy Analytics. Samsung was a distant second with 400,000 shipped and a 7.5 percent market share.

However, the market is still nascent, and Apple Watch isn't an option for people who use Android smartphones.

Samsung's Gear S2 will work on Android - and for the first time, not just Samsung's Android phones. Meanwhile, watches running Google's Android Wear software will now work with Apple's iPhones.

The limited selection of apps is one of the main challenges facing Samsung's smartwatches. They have been around for longer than the Apple Watch but haven't generated as much interest or sales.

Samsung's newest, the Gear S2, faces competition not just from Apple but also from a variety of manufacturers using Google's Android Wear software. According to IDC, Apple was the No. 2 maker of wearable devices in the April-June quarter, with a 20 percent worldwide market share, behind the Fitbit and its fitness trackers at 24 percent. Samsung was fifth with 3.3 percent.

First previewed during last week's Samsung Unpacked event, the Gear S2 smartwatch has now seen its teaser trailer plastered over YouTube.

Although offering no new details on the device set to go head-to-head with the likes of the Moto 360 and the LG G Watch R, the teaser video provides our first HD look at the stunningly styled wearable.

Set to run a reworked version of the company's Tizen OS, Samsung has bestowed the Gear S2 with an integrated heart rate sensor and microphone that lets it double as a hands-free calling enabler.