We value Open Source and make a point to release all our plugins on GitHub under a BSD License.
The WakaTime plugin works for Visual Studio for Mac, MonoDevelop, Xamarin Studio and is open source on GitHub.
Inside MonoDevelop/Xamarin Studio navigate to Tools → Add-in Manager.
(Visual Studio → Extensions… in Visual Studio for Mac)
Click the Gallery tab, then search for wakatime.
Click the Install button and then when add-in installation dialog popups click Install.
On MonoDevelop/Xamarin Studio versions prior to 5.10 you might get an error message, just ignore it.
Enter your API Key, then click Apply.
You might have to restart your IDE.
Use your IDE like you normally do and your coding activity will be displayed on your WakaTime Dashboard.