I have found a solution. In some ways it is better in others it's not.
I have found an application - "Media Zone Trigger". When combining this with a webcam the program displays a media file, when movement is detected inside a hotspot of your own choosing. I have just started testing it out, but here are my first experiences;
- It seems you can choose multiple hotspots, and choose different mediafiles to be triggered to the different hotspots (or a combination of hotspots?).
- sensitivity can be adjusted
- It can, as far as I can see, only display images and movies.
- 1 license is for 1 computer only, making it rather expensive at 250$ per license.
- It will not work when there's no light. This could be useful for displays facing streets.