Detect lack of user activity

[iainc.dev]

Is there a way in SmartGWT to detect that there has been no user activity for "x" minutes? For us, no user activity can be defined as "no mouse click" in our SmartGWT app? If so, how can this be done? (Any examples would be helpful, as usual).

Also, if this can be done, would the technique still work (that is, still detect mouse clicks) even when a user is clicking inside an "iframe" that sits inside our SmartGWT app (and this iframe points to the same domain as our normal SmartGWT app, but a different port that is ultimately mapped to a different computer server).

Here's my standard additional background info:
======================
SmartGWT (not smartclient) Version: SmartClient Version: v8.3p_2012-11-26/PowerEdition Deployment (built 2012-11-26)
...
Browser: Firefox 29 on Mac 10.9.2
GWT SDK: 2.5.0rc2
Sun JDK 1.6.0_13
J2EE: Tomcat 6
OS: Centos 6.x

[Isomorphic]

One way to do this would be to use a GWT EventPreview handler to get a notification of all click events anywhere in the page.