The LG G Watch and the Samsung Gear Live both went on sale Monday, providing the first test for Google's just-for-wearables version of its mobile operating system, called Android Wear. The launch marks Google's first big push into wearables market as it tries to get ahead of potential competitors, such as Apple, and convince consumers that these wearable devices are actually worth getting.

Both boast a host of features that Google showed off at its recent developers conference, such as the ability to make and take calls, run a Google search or order a cab from Lyft by asking your watch, and get real-time traffic updates delivered to your wrist.  But there are a few differences between the two models. The main one is price: Samsung's Gear Live costs $199.99, while the LG G Watch is $229. Customers who put down the extra cash for the LG G Watch should get a little more juice per charge due to the G Watch's larger battery. The Gear Live sports a built-in heart monitor that the LG G Watch doesn't, although both have a pedometer.

One thing you should remember before buying: Pick up any smartwatch and you're likely signing up to share even more personal data with Google. That's not necessarily a bad thing -- the extra data collection lets you make the most of the device's features -- but it's good to remember that the things that really distinguish wearables from smartphones rely a lot on picking up extra data.

Step count and heart rate data are just the beginning. Android Wear comes with "Google Now," the tracking and notification application that Google's had on smartphones for a while, completely baked into the system. That makes your watch your personal assistant, which can do a lot for you if you let it: Android Wear will offer you traffic-based time estimates for your commute, make reminders that pop-up when you get to your office or your home, send e-mail and even take dictation. All of those systems, though, plug you ever-deeper into the Google ecosystem -- notes go to Google Keep, directions come from Google Maps -- and while that's not surprising, it is something that users should know about before signing on.

If a Google-run life sounds great to you -- let's be honest, a lot of us are already there -- there are still a few more things to consider before you buy. Unless you're really, really into the whole smartwatch thing, you may want to hold off for now, reviewers say. These devices still require a smartphone to work -- and cost just about as much as a smartphone -- and not everyone thinks they deliver on the full promise of wearable just yet.