Please, take a look at the Custom Services SDK example
of RadDiagram and let me know if it works for you. The example demonstrates implementing of few custom services including DraggingService that can restrict the drag of the shapes in a predefined rectangle
Check out Telerik Analytics, the service which allows developers to discover app usage patterns, analyze user data, log exceptions, solve problems and profile application performance at run time. Watch the videos
and start improving your app based on facts, not hunches.