Don't get all excited, this does nothing more than wrap SmokePing in an iframe and display it with it's own tab in Cacti. For the most part, it is just the ntop plugin with ntop replaced with smokeping.
To use it, just unzip the attachment into your plugins directory, add the appropriate line to global.php, and set the URL of your smokeping server in Settings -> Misc -> SmokePing. Add SmokePing to your user(s) in User Managerment and you should see a SmokePing tab appear.
I really want to do a better integration of this, but this is all I have time for at the moment. It isn't perfect, but it's better than yet another web interface that I have to track somewhere else.