Even sillier than the the Serial cable surge suppressor is the APC AP9324... Alarm Beacon.
Part of the NetBotz series of products, this alarm beacon will "Quickly notify personnel of critical situations with a visible alarm signal"
Mercifully, it does not have an alarm or buzzer. But in a pinch it can be turn your server room into a rave den. Obviously people like this item, as its offered by hundreds of suppliers and is actually ranked 40,000 or so in electronics at Amazon.