It's a hot stone (steak stone), although I personally wouldn't cook in front of my computer, last time I used one in a restaurant they gave us bibs to wear, lol.
http://www.steakstones.com/
Indeed, mine is this one:
http://www.steakstones.com/shop/bamboo-range/the-steakstones-sizzling-steak-plate-set/
I would invest in some gloves though, oven gloves will burn if you pick the rock up with them. You have been warned.