I found this Power Meter on BangGood for only $20. It is more advanced than the previous meter I used and has a large Color display that is easy to read. It has USB3 and Micro USB connecting points. In addition to the multiple display’s to monitor different functions it also has a BT connection that will connect to the companion app in your phone. The manual and app are both available on the web site from the link on the enclosed card and the instructions in English are easy to follow. Other languages are also available for the device.
So what do you actually get out that? Doesn’t the watch let you know when it is fully charged? I mean what more do you need to know?