Shenzen?
When I look at their manual (http://www.u8watch.net/U8-usermanual-en.pdf ) and install the 'BT Notification.apk' - connects to: APK Access mode:Downloaded from Web address
IP Address: http://www.chrsz.com which is 116.204.15.137. http://www.chrsz.com/classpro/index/183
a geolocation of that ip shows it to be: Shenzhen, China. which would be Shenzhen Coheretech Co., Ltd.
I wonder if thats where the connections are headed to: http://ipinfo.io/AS17962