Wear Compass Pro is a simple app that brings a nice looking compass on your Smartwatch (Android Wear device for example Moto 360) or you also use the app on your Android smartphone.
It always shows you the direction to magnetic north and also the strength of the magnetic field in your area (in micro Tesla).
The app uses the internal magnetic field and accelerometer sensors to calculate magnetic north. (please be aware that the accuracy will be influenced by other electronic devices or iron stuff)
To use the app on your smartphone, you need at least Android Version 4.0.3. And to use it on an Android Wear device you need Android 4.3.1 on your phone and 4.4 or higher on your watch.
You can download it from here: https://play.google.com/store/apps/details?id=at.bonlabs.wearcompass