With Mango for Windows Phone we have some cool changes for the system tray control. SystemTray is a DependencyObject and because Mango is now running on SL4, DependencyObject can be data bound. The other feature for the System Tray coming with Mango is a ProgressIndicator which can used to display progress on async operations.
More details and sample code about the new ProgressIndicator in the System Tray you can find here: System Tray Progress Indicator - Jaime Rodriguez - Site Home - MSDN Blogs
Data Binding of ProgressIndicator
Sample for programmatically data binding of the ProgressIndicator in the Loaded-Event of the page:
Updated: Data Binding over declaration
Many thanks to a colleague, who give me the tip that data binding for SystemTray is also possible with XAML declaration.