SQL Server Query Notifications is a great tool, but it doesn't seem built to scale very well. Every application that wants/needs notifications has to keep an open connection to the database for the duration of the time it wants notifications (typically the entire time the application is running).
I am open to creative solutions. Off the top of my head I just thought of putting a service on the server that would subscribe to SQL Server Query Notifications which could then notify the client applications. In this case you have only 1 database connection open (and why not just leave it open all the time), and then your client applications could just subscribe to the service for notification.
Ideas??