We've recently acquired a Tripp Lite PDUMH20AT-NET, which is a power-switching appliance. We're using it at our data center, where there was a recent PDU failure. Since we were on the PDU that failed, and we only had power connections to that single PDU, we lost all of our systems.
Going forward, we've added a second PDU circuit to our rack and have the Tripp Lite PDU switch for our single-power supply systems such as switches and a couple routers. Having this unit would help mitigate further problems, but as this unit supports SNMP monitoring, I've written a script that allows Nagios to poll via SNMP the input and output voltages, frequency, and output current.
In addition, check out the PDU Cacti page for the cacti graphs I've created, along with the perl script to go along with it.