Apple GateKeeper Dialog Box
FocusTune is fully comparable with macOS Sierra, however, changes to the Apple Gatekeeper may force an extra dialog box to be clicked each time when launching FocusTune.
Copy FocusTune.app to Applications folder
After downloading FocusTune, the zip file should be uncompressed (double-click). Then FocusTune.app should be copied to the Applications folder. The downloaded version and the zip file can then be moved to the Trash.
This video explains how to download and run FocusTune.app under macOS Sierra.