Desktop notifier plus browser based chat (server side in .NET and client side across Windows, Mac, Linux)

Hi, I want a prototype of a desktop notifier which I can install on my team's desktops so that when my customers send a message to us from a page on our website, it notifies some of our team members based on pre-defined rules (eg all of our marketing people receive the notification if the customer sends a message to marketing). If any of the receivers of the notification clicks on the notification, that shd trigger a browser based chat session between the customer and them. For each of the receivers, if they dont click on the notification, the notification should just slide back down and disappear. The messages being sent by our customers through our website as well as any chat sessions need to be recorded so that we can access them later. The notification as well as the chat app need to work across Windows, Mac and Linux. This needs to be done using .NET on the server side. On the client side (notification), the app needs to work across Windows, Mac and Linux. Also we host our website on a shared server (.NET 2.0), so it needs to run in that environment on the server side. Thanks