Simple (hardware) Watch Dog Timer for Arduino Projects

We all use and love the Arduino boards for our projects. But sometimes it can happen, that a software or hardware error causes a lot of frustration, by stopping out little board from running 24/7.
For this reason Arduino has a built in WDT (Watch Dog Timer), but in some of my projects (working a lot with external libraries) I found that the on-board solution doesn’t always work as expected.
To resolve this issue, I have designed a simple external WDT, to monitor my project and reset the board if it seems to be stuck somewhere.”