This is not a breath-taking idea, and it could be already implemented, but nevertheless it deserves couple lines of text here.
This a client-server application, which integrates with OS, and alerts user when new software/hardware updates are available for him or her. This application should cover as many applications as possible. Software developers could use Update Manager's server to inform users about updates or plans. Moreover, Update Manager can optionally inform owner about program- vendor- related news.
Why this application will be useful for users? It's easy - no need to update software one by one. Everything is centralized.
You can object with (at least) one word: Privacy. Yep, but if vendor of this application is trusted, like Google (or Microsoft if you wish) then I see no problems :).
No, something is wrong with this idea. For some reasons I don't like it in the end of the post :). Maybe you could proceed with it and get golden eggs.