I've been using xDrip+ and G5 for 6 months now. It's great. Like part of me now.
As
@tim2000s said, it supports Android Wear watches natively. I chose the Sony Smartwatch 3, because that's the device that the developer of the Wear integration part uses. I just works.
I have the watch acting as a standalone collector for the G5 data. This way, you don't even have to take your phone with you to see current BG readings, or even to record carbs and insulin doses. It's very reliable, and I hardly miss any readings at all. Initially, I just had xDrip running on the phone, but I would invariably miss readings after wandering away from the phone.
The watch battery easily lasts all day.
Another cool feature is that you can pair xDrip with a bluetooth glucose meter (eg. Contour Next One), and blood test go straight into xDrip without having to type them in. One of the issues with CGM is knowing when to use blood tests to calibrate. You can choose to have xDrip decide for you automatically whether to use the BG readings it gets from the meter for calibration.