Motion detection

You can use the Video macro condition for motion detection.
In general, you should use the "has changed" check type of the video condition for this purpose.

When using the default settings even the slightest change anywhere in the sources output will trigger this condition.

This might not lead to the desired effect as some video sources can contain a slight amount of "noise" in the video output which would trigger the condition even if nothing much has changed.
To tackle this you can use "pattern matching" to ignore small changes in the video output.

Additionally you can specify if you would only like to check for changes in certain parts of the video output generated by a source.
To do so check the "Perform check only in area" option and select the area you want limit the check to.

If you want the condition to only trigger if changes were observed for a certain amount of time you can add a duration modifier to the video condition.