Google's (NASDAQ:GOOG) (NASDAQ:GOOGL) Android operating systems powers smartphones in all manner of shapes and sizes. Starting this fall, the same will hold true for smart watches.

Android Wear -- the version of Android designed for smart watches -- will soon be available on a wide variety of watches from a plethora of manufacturers: LG, Asus, Motorola, Sony, and Samsung will have models out for shoppers to purchase this fall.

Asus brings Zen to the wrist
Asus, widely known for its line of Zenbook laptops, plans to release an Android Wear watch sometime in the next few months. The device, named the ZenWatch, has a rectangular, curved watch face with a stainless steel backing.

Like virtually all Android Wear devices, Asus' watch sports a heart rate monitor and pedometer, and ties in directly with Asus' fitness tracking software. But it does have a few unique features -- by making use of Asus' ZenWatch Manager app, owners can control their smartphone's camera remotely, or wake their phone up by double tapping on the ZenWatch's screen.

Asus ZenWatch. Source:

Motorola's Moto 360 is finally here
Announced back in March, Motorola's Moto 360 is finally on sale. Motorola's watch may be the best looking of the bunch, with a thin bezel and traditional design. The watch face itself is made of stainless steel, and customers that are willing to wait a few more weeks will be able to purchase one with a steel band rather than the leather strap that ships with the watch by default. At $249 ($299 with the steel band) Motorola is pricing its device competitively.

Yet it does suffer from a number of flaws -- in particular, battery life. Reviewers have almost universally found fault with the Moto 360's battery, which seems to run out of juice in less than a day. At the same time, Google's Android Wear seems to have been designed for rectangular watches, rather than round ones, leading to the occasional cut-off menu.

Moto 360. Source:

LG: Forget about the first one
That shouldn't be a problem for too much longer: Given the growing popularity of circular Android Wear devices, it would surprising if Google didn't update the software at some point in the near future.

As an alternative to the Moto 360, LG plans to offer a round watch of its own. The company's first smartwatch -- the LG G Watch -- was one of the first Android Wear devices ever released. LG, however, does not seem particularly proud of the effort, and less than six months later, is preparing a second G Watch, the G Watch R.

Compared to the Moto 360, the G Watch R offers a faster processor and more water resistance (unlike the Moto 360, the G Watch R can be submerged under water). Its display is fully circular, but unfortunately, has particularly thick bezels. LG has said the watch's battery should last two days before it needs a charge, which would be an improvement over the Moto 360, but that remains to be seen.

Final pricing and availability of the G Watch R have not been announced, though it is expected to go on sale at some point next month.

Sony SmartWatch 3. Source:

Sony changes its mind
Sony has been offering Android-powered smart watches for years. Its first-generation SmartWatch, and second-generation SmartWatch 2, were powered by modified versions of the Android operating system. When Google unveiled Android Wear earlier this year, Sony's management made some comments suggesting that they would stick with their own software efforts rather than embrace Google's.

The Japanese electronics giant, however, seems to have changed its mind. Unlike its predecessors, Sony's SmartWatch 3 is running Google's Android Wear. Compared to its peers, Sony's watch is far more sporty -- rather than steel or leather, its strap is made of brightly colored silicon.

It's also more rugged -- its IP68 rating means that it can survive underwater at a depth of more than six feet (better than LG's G Watch R). Sony has said it will add a custom Walkman app to the phone, which may allow it to function as an mp3 player (it's equipped with 4GB of internal storage). Paired with Sony's new, waterproof Bluetooth headphones, it could carve out a niche among swimmers, or athletes in general.

Samsung Gear Live. Source:

Samsung continues with Tizen
Samsung's Gear Live is its Android Wear-powered smart watch. It went on sale in July, and should still be available for purchase later this year. Compared to the other watches on this list, it might be the least attractive, and has few distinguishing features. But at just $199, it is the cheapest.

Samsung would probably prefer customers opted for one of its other watches. The Gear S, which is expected to debut next month, runs Tizen -- not Android Wear. Unlike Android Wear devices, it isn't compatible with just any handset running an updated version of Google's Android -- owners need a Samsung-made phone to get the most out of it. The Gear S offers similar functionality to Android Wear devices, but is far more advanced. Equipped with a 3G modem, Samsung's watch can make and receive calls and texts even when it isn't paired to a phone.

Android's strength
The strength of Google's mobile ecosystem lies in the wide variety of options it endears. While no single device may be perfect for everyone, many should find something to like among the various choices. In time, the sheer number, and variety, of Android Wear devices should only increase.

Sam Mattera has no position in any stocks mentioned. The Motley Fool recommends Apple, Google (A shares), and Google (C shares). The Motley Fool owns shares of Apple, Google (A shares), and Google (C shares). Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.