diff --git a/actions/sup.php b/actions/sup.php
new file mode 100644
index 0000000000..887017b2a4
--- /dev/null
+++ b/actions/sup.php
@@ -0,0 +1,81 @@
+<?php
+/*
+ * Laconica - a distributed open-source microblogging tool
+ * Copyright (C) 2008, Controlez-Vous, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+if (!defined('LACONICA')) { exit(1); }
+
+class SupAction extends Action {
+	
+	function handle($args) {
+		
+		parent::handle($args);
+		
+		$seconds = $this->trimmed('seconds');
+		
+		if (!$seconds) {
+			$seconds = 15;
+		}
+
+		$updates = $this->get_updates($seconds);
+		
+		header('Content-Type: application/json; charset=utf-8');
+		
+		print json_encode(array('updated_time' => date('c'),
+								'since_time' => date('c', time() - $seconds),
+								'available_periods' => $this->available_periods(),
+								'period' => $seconds,
+								'updates' => $updates));
+	}
+	
+	function available_periods() {
+		static $periods = array(86400, 43200, 21600, 7200,
+								3600, 1800,	600, 300, 120,
+								60, 30, 15); 
+		$available = array();
+		foreach ($periods as $period) {
+			$available[$period] = common_local_url('sup',
+												   array('seconds' => $period));
+		}
+		
+		return $available;
+	}
+	
+	function get_updates($seconds) {
+		$notice = new Notice();
+
+		# XXX: cache this. Depends on how big this protocol becomes;
+		# Re-doing this query every 15 seconds isn't the end of the world.
+
+		$notice->query('SELECT profile_id, max(id) AS max_id ' .
+					   'FROM notice ' .
+					   'WHERE created > (now() - ' . $seconds . ') ' .
+					   'GROUP BY profile_id');
+		
+		$updates = array();
+		
+		while ($notice->fetch()) {
+			$updates[] = array($notice->profile_id, $notice->max_id);
+		}
+		
+		return $updates;
+	}
+	
+	function is_readonly() {
+		return true;
+	}
+}