I think it would be beautiful to have an indicator in Unity tray, counting Google+ notifications (orange on black, like in Google bar). Where can I find it?
As already mentioned in a comment:
Currently the google+ API seems not to allow access to the notifications. There is a feature request here which asks for exactly this API enhancement. So it is unlikely that a desktop application will provide this, as long as the API is missing.
The exceptions to this seem to maintain a hidden webkit window, which is first used to login the user and later does ajax calls to the google+ website plus probably some screen scraping of the result. This is not a straight forward way of handling something that would only require a simple API call in case it was enabled. So most developers will probably wait until the API is updated.