This post describes quite well what is needed to implement this mechanism (of course, YUI is not needed): http://www.nczonline.net/blog/2009/06/02/detecting-if-the-user-is-idle-with-javascript-and-yui-3/

Implemented user-inactivity detection feature. The feature introduces ice.onUserInactivity function that can be used to register callbacks with. These callbacks will be invoked after the passed in interval of user inactivity has elapsed.

For example:

ice.onUserInactivity(45, function() {
   alert('Do you want to save the data you entered?');
});

The code above registers a callback that will be invoked after 45 seconds of inactivity.

There are a couple of reasons why the timeout interval is specified when ice.onUserInactivity invoked instead of using icecore:config tag:

a) The application might choose to alert the user multiple times at different intervals. Maybe an action will need to be taken once the last alert was shown for a while.

b) Defining the interval in icecore:config makes the configuration disconnected from the actual API use. The application code can always read a parameter or use a value binding to acquire the interval and then register the callback using the interval value.

After reviewing common use-cases, it seems that expanding this feature slightly to also support optional callback notification if a previously idle user becomes active is warranted.

For example:

ice.onUserInactivity(45, showIdleDialog(), hideIdleDialog() );

...would display a dialog when the user goes into the idle state, and hide the dialog if/when the user returned to active status (after first going into an idle state).

Having both callbacks would enable the type of scenario depicted above, as well as possibly some interesting "background" JS processing that components may perform when the user is deemed to be idle.

Modified API and implementation to account for the active user callback.

Added API docs to the Wiki: http://www.icesoft.org/wiki/display/ICE/JavaScript+Client+API