Motorola debuts second-gen Moto 360 smartwatch, first-gen Moto 360 Sport

Unlike its predecessor, the updated flagship 360 will come in two different sizes, 42 and 46 millimeters. The first has a 1.37-inch, 360-by-325-pixel display, while the second scales to 1.56 inches and 360-by-330 pixels. Both Watches are equipped with 1.2-gigahertz quad-core processors, 512 megabytes of RAM, and 4 gigabytes of onboard storage.

The 42-millimeter model should last up to one and a half days on a single charge, while the 46-millimeter one can last up to two days.

The watch is also launching with a wide variety of case, bezel, and band options for men and women. Men's cases are available in silver, black, or gold, for instance, with chamfered or "micro-knurl" bezels, and bands in one of three metal colors or two leather ones.

Though still based on Google's Android Wear — which now has limited iPhone compatibility — one unique Motorola software feature is "Live Dial" faces, allowing people to open apps or use their features without scrolling through menus.

The new Moto 360 should ship later in September, starting at a cost of $299, and can be preordered today.

Still partly shrouded in secrecy is the Moto 360 Sport. The device uses a 42-millimeter display, but features silicone exterior materials in order to make it more resilient against heat and sweat. It also has built-in GPS for tracking running and walking without a smartphone.

New screen illumination technology dubbed AnyLight should make the device easier to use outdoors. Although in many cases the watch relies on regular LCD backlighting, under intense conditions, the Sport can automatically flip to natural front lighting to make text more legible.

Pricing and a release date for the Sport have yet to be announced.