Xperos for macOS
Xperos has a fully native macOS client written in Swift! This includes the ability to put a timer in the status bar displaying how long your current fast has lasted.
The main window where you will likely spend your time (pun intended) is your timer, which displays quick information about your current fast — and if you don't have one going, you can start a new one. And it supports Mojave's new Dark Mode!
The progress bar above the Start/End Fast button gives you a visual idea of how far along you are with your fast — and you can always keep fasting after the bar is full.
The history view gives you a native macOS view of your fasting data, enabling you to peek back at the full history of your fasts, as well as make any corrections necessary to data.
The toggleable sidebar shows the information about the currently selected fast, letting you edit it and save it as necessary. If you wish to delete a fast, right click on it.
In Preferences, you can turn on a feature that will make an Xperos icon always show in the status bar. During fasts, this will show the timer as well. Additionally, this provides a quick menu for toggling your fast as well as bringing up the Timer or History view.