Wall socket equipment power on/off notifications via email/SMS?

I have a warehouse full of widgets plugged into power outlets. These widgets are dumb devices that don't run software; they just draw power from the wall socket. I need to know which widget has been turned on or off, and when it started and stopped pulling power.

Ideally, a device that sat in the circuit between the wall socket and the widget would send an email when power was applied, and again when power was turned off.

It could be an even dumber device that simply sent pings to an email address, from which the time of power on/off could be extrapolated.

A UPS with a network card, or something like an iSocket, is more than necessary in terms of features and cost.

I could probably create this device with a Raspberry Pi or Arduino and an XBee, but I'd rather get mass-produced off-the-shelf units of they exist.