App variable Update to ViewModel

Hi guys i have a question regarding the propagation of changes to variables declared in the App class to the UI.

I Have a method in OnStart() that periodically checks that my data is synced with a web service and returns the result as

Syncstatus. How do i detect changes to Syncstatus on the Viewmodel

This will grab the initial value but updates are not Reflected.

    public string Syncstatus
    {
        get
        {
          return App.SyncStatus;
        }
    }

Any help will be greatly appreciated

Best Regards.

WIL