The WakaTime plugin works for both MonoDevelop and Xamarin Studio and is open-source on GitHub.
Inside MonoDevelop/Xamarin Studio, navigate to Tools → Add-in Manager.
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 MonoDevelop/Xamarin Studio.
Use MonoDevelop/Xamarin Studio like you normally do. Your programming activity will be tracked for you automatically.
Visit https://wakatime.com/dashboard to see your logged time.