USBmicro is a USB electrical device interface. It comes in two flavours: the U401 and the U421. The main difference is the form factor.

There’s quite a lot of documentation on the site how to program and install them

Kadtronix sells the unit with interface software, making the programming quite a bit easier

They also have a good tutorial, with instructions how to fit it to a motion detector

Home Domination has the controller and bundles it with several types of sensors, such as temperature sensors and it’s own software

But if you just want to buy the units themselves, they’re not expensive at around EUR. 28,- at dontronics