Yoctopuce Yocto Watchdog DC
This device is a USB-controlled watchdog timer. When installed across a DC power cable, it can cut and restore the power whenever the control application fails to contact it.
The typical application is to power-cycle a crashed computer. As long the control application running on the the computer contacts the device on a regular basis, the power stays on. If, for some reason, the application stops to contact the device, the power will be cut for a short time. The will cause the computer to reboot.
This device can also be used as a cheap solid-state relay. Please note that this device is not isolated: the output and the USB share the same ground.