DomJudge_Room.user.js

// ==UserScript==
// @name           DomJudge IP
// @namespace      http://nullrich.de
// @include        http://domjudge.iti.uni-karlsruhe.de/*/submissions.php*
// @require        https://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js
// ==/UserScript==

function deserialize(name, def) {
  return eval(GM_getValue(name, (def || '({})')));
}

function serialize(name, val) {
  GM_setValue(name, uneval(val));
}

var cache = deserialize('ip-cache');

$('#refresh').append('<input type="button" value="Clear IP cache">').click(function() {
	GM_log("bwaaaa");
	cache = {};
	serialize('ip-cache', cache);
});

$('th:nth-child(3)').after('<th scope="col">ip</th>');
$('td:nth-child(3)').each(function(index) {
	var name = $(this).attr('title').split(':')[0];
	var tr = $(this).after('<tr/>');

	if (cache[name] !== undefined)
		tr.after($('<tr/>').html(cache[name]));
	else
		jQuery.get('team.php?id=' + name, function(data) {
			var ip = /i08ppc([0-9]{2}).atis-stud.uni-karlsruhe.de/.exec(data);
			if (ip) ip = parseInt(ip[1]);
			cache[name] = ip;
			serialize('ip-cache', cache);
			tr.after($('<tr/>').html(ip));
		});
});