@dstoneham Do you have a screen with CCFL or LED backlight. If CCFL you could try to replace with a LED strip and see how that works. You can those very cheap already. I did that with an old 17" LCD which had 4 CCFL tubes. Now it has 2 LED strips instead and the brightness increased.

@canberra The display should at least power off once there’s no HDMI signal detected anymore. It’s a bit weird it doesn’t do it in your case. However, it wouldn’t power back on after the HDMI port has been activated again. Therefore you’ll need a relay for sure.
It’s working really great in my case. I’ve got the PIR-sensor and the relays from AliExpress for just a couple of cents. You can also try those 12V PIR-Sensors, that you plug in between the power supply and your LCD controller board. It’s not working in my case, though. Looks like some signal noise keeps it awake all the time.

@canberra Can you tell us what controller board exactly you have? You mentioned a remote. Is it correct to assume you a universal controller board like the V56 boards? If so, you’ll need an extra relay to power on/off the display. Although it should power off normally once there’s no HDMI signal anymore. @cruunnerr wrote a very detailed guide on how to use a PIR sensor with your mirror. It offers lots of possible pathways and they are very well explained. Have a look.

Offtopic: Even with a broken English you might get better help than asking in German only.

I suspected this module for a while already but I never bothered to get into it. Whenever somebody reported random crashes after some hours they used the MMM-GoogleMapsTraffic module. In my case it is enough to run a cronjob once a day to reload the mirror.

@lorcalhost This german shop also ships to Italy. The prices for the mirrors are pretty good. Shipping costs to Italy are:
up to 2,000 kg: 14,50 €
from 2,001 kg up to 10,000 kg: 24,50 €
from 10,001 kg up to 20,000 kg: 29,50 €
from 20,001 kg up to 31,500 kg: 40,00 €
from 31,501 kg: 150,00 €

The Pilkington MirroView might be the best option for a smart mirror. I currently have the Mirropane Chrome Spy with only 8% transmission which I will replace before summer with the MirroView (20% transmission and higher reflection).

I am considerung buying an android TV box to run MM on. They are cheaper and - at least on paper - more performant than the RasPi (faster cores, more RAM, onboard storage). Those are generally Amlogic based.

Has anyone tried that before? All I found way other users asking but nobody seemed to tested it AND posted it here.

@pakmann Thank you for testing and sharing your results. I already had the suspicion that it was the MMM-GoogleMapsTraffic module as it was used by a lot of users that faced the very same problem.

Of course it runs on a Pi. Even a Pi0. You can either directly use OpenElec, an SD card image that runs Kodi directly, or install it via sudo apt-get install kodi. It’s a general mediaplayer that can also display pictures and shuffle through them. Though, I don’t know how to set it up to load the pictures automatically after booting. That’s what you’ll have to find out.

Not sure if that’s exactly what you’re looking for but have you tried Kodi?

View from the back:

View from the front:

PIR sensor without IR lense and the inside-8mm-hole: