jquery.wake.coffee

$        = jQuery
TIMEOUT  = 20000
lastTime = (new Date()).getTime()

setInterval ->
  currentTime = (new Date()).getTime()

  # If timeout was paused (ignoring small
  # variations) then trigger the 'wake' event
  if currentTime > (lastTime + TIMEOUT + 2000)
    $(document).wake()

  lastTime = currentTime
, TIMEOUT

$.fn.wake = (callback) ->
  if typeof callback is 'function'
    $(this).on('wake', callback)
  else
    $(this).trigger('wake', arguments...)

jquery.wake.js

(function($){

var TIMEOUT = 20000;
var lastTime = (new Date()).getTime();

setInterval(function() {
  var currentTime = (new Date()).getTime();
  if (currentTime > (lastTime + TIMEOUT + 2000)) {
    $(document).wake();
  }
  lastTime = currentTime;
}, TIMEOUT);

$.fn.wake = function(callback) {
  if (typeof callback === 'function') {
    return $(this).on('wake', callback);
  } else {
    return $(this).trigger('wake');
  }
};

})(jQuery);

It appears that some do. Chrome/Firefox limit the setInterval time to around 1000 ms. IE/Safari/Opera have no restrictions. However, according to this that may not be true on iOS. For a more in depth explanation read this StackOverflow Post.

WakeUp is a jQuery library that does the same thing. I recommend combining this with the changes recommended by acdha above.