[peterburkimsher]

Slightly off-topic, but I've been wanting an HDMI Freeze button for a while.

I looked at the auvidea link that kayfox suggested, and could probably implement it in software on an RPi. But that has limited resolution and frame rate (25 fps).

For a feature built into most projectors, I'm surprised there's no products to do this.

[kayfox]

The resolution and framerate issues with that solution appear to be software implementation limitations, I haven't looked into them, but I would expect they could be resolved, since they appear to be an artifact of just one developers environment being tested against.