Relay for dry contact control that runs off USB (5VDC)?

Actually, I know of two devices that might fit the bill, and both use Zigbee. The first is @iharyadi’s awesome little environment sensor that I believe may have the option to control a digital output pin connected to a standard dry contact relay. The second is @drandyhaas’ very cool Mona Lisa board, which I am certain can control a few digital output pins.

Neither of these are truly commercial off the shelf offerings, but they are pretty cool devices, and both are fairly small. Both are powered by 5VDC.