I also have had success using Xdrip with a Sony Smartwatch 3 as a direct receiver for the Dexcom G5 and I have successfully installed the patched firmware to allow an Asus Zenwatch 3 to work as a receiver. The Zenwatch 3 is a much nicer looking watch, but the Sony is MUCH easier to use since installing the patched firmware is somewhat complicated and the instructions are not very good.
I don’t think either watch is in production anymore, but they are relatively easy to find on eBay. I got the Smartwatch 3 (SWR50) for $60 on eBay and the Zenwatch 3 for $110, although they typically go for a bit more than that.
Dexcom’s solution for using a smartwatch is incredibly stupid, but has the advantage of working with pretty much any smart watch. Briefly, with Dexcom’s solution you need a supporter phone that receives the data from the transmitter and uploads it to Dexcom’s server in the cloud. Then the smartwatch connects to the phone and uses it to connect to Dexcom and download the data from the cloud to display it. This means you use twice as much bandwidth (uploading the data and then downloading the exact same data) plus if you are on an airplane, or your phone is otherwise not connected to the internet, your watch won’t display anything. Stupid solution created by lazy programmers.
xDrip is a much more elegant solution, especially if you have a watch that can work as a data collector, although getting the watch to work as a data collector can be a bit tricky.