In Qt4, does anybody have a good idea of how determine if there is no user interaction with a program?

I'd like to have a have a signal emited if the user has been inactive for x minutes. I was thinking I could have a single shot qtimer that is reset after any user event, by a installEventFilter function for the qmainwindow. Would this work? Is it the best solution. I wanted to get some advice before I ran off and spent a bunch of time playing. Thanks.