Im using this:

https://github.com/ehynds/jquery-idle-timeout

It can display a notification after X number of seconds/minutes since the last mouse/keyboard movement on the page. This is very helpful so it doesn't get in the way if a user has been on a page for a while typing lots of text etc... A normal timeout would get in the way and interrupt the user after X seconds. The notification gives the user X amount of seconds to decide if they are wanting to log out or stay on the page. If they don't answer within X seconds it auto redirects them to a locked page.

For me the locked page gets the user object, logs them out and displays a locked page with their email auto filled, just waiting for a password.

Works very well

Theres a good demo on this template. http://www.keenthemes.com/preview/metronic/theme/templates/admin/ui_idle_timeout.html