WatchCheck is an Android app in Material Design to easily measure the precision of mechanical watches.
The speciality of WatchCheck is, that as reference time only precise time sources such as NTP (network time protocol) and GPS are used, but never the imprecise internal clock of your device (mobile phone or tablet). With GPS you can do precise measurings even when there's no data network available, e.g. when you're abroad.
If you worry about the "precise location" right, it is required only for retrieving the accurate reference time via GPS in case you don't have network access.