One of the problems with being a computer lab instructor is that you frequently need to leave your computer to help one of the students. During the time, the computer may still be logged into your account and available to any of the other students. They may see something they ought not to or send the administration your resignation letter.
The Wireless PC Lock is a device that attaches to your computer via a USB port. A second device sends out a radio signal letting the device connected to the USB port that you are at the computer. When you move away, the device locks the computer. Apparently, the software that comes with the hardware is not very good but an open source project has created software that greatly improves the functionality. The hardware costs about $40 and the software is free.
Below is a link that describes the system and where to get the improved software.
Monkeys are very furious - USBWiSec: "Bryan Batchelder is the Head of Research & Development for PatchAdvisor, Inc - A vulnerability intelligence provider and security assessment company. "