(function( $ ) {

$.pi = $.extend($.pi, {
    expire : function( fn, callback, interval, start ) {
        var timer;
        function set() {
            timer = setTimeout( callback, interval );
        }
        if (start) 
            set();
        return function() {
            clearTimeout( timer );
            set();
            fn.apply( this, arguments );
        };
    },
    ajaxExpire : function( callback, interval, start ) {
        $.ajax = $.pi.expire( $.ajax, callback, interval, start );
    }
});

})( jQuery );