[natebleker]

It would be really cool to add facial recognition at like 0.5hz to the phone so that it only turns the screen on when you're looking at it. Or alternatively customize the content based on who's present in front of the mirror.

[iverjo]

Alternatively, one can use a thermal sensor, like I did in this project [1], where the light is turned on when somebody is standing still in front of the mirror

[1] https://github.com/iver56/auto-light

[artmageddon]

Maybe add a motion sensor to it?

[Raphmedia]

Perhaps a light sensor? You are not going to use your mirror in a dark room. Unless you want the display to show up in the dark, but personally I wouldn't want that.

[CydeWeys]

That wouldn't work during the day if your bathroom has a window (it'd be on all day).

I think the simplest way to do it would be to tie it in directly to your light switch. (Note that the light switch wouldn't be controlling power to the Android device, it would merely be a data signal determining whether the display should be on.)

[Raphmedia]

I'm used to small bathrooms with no windows.

If you have a window, tying it to the light switch would be ideal. Or you could simply add a small button next to the light switch.

[artmageddon]

Right, but you may not want the mirror to always be on just because you're standing out of it's viewing angle in the same room at 11PM when the moon is out. Maybe a combination of light and motion sensors..?

[irl_zebra]

Motion sensing seems like a better solution to me. I can imagine looking from diagonally across the room wanting a quick glance at the current temp outside and it not showing up because it doesn't see my face.

[natebleker]

Solid point. Maybe just a cheap wide angle lens from ebay and use easy off the shelf background subtraction from opencv at a low frequency as an easy of motion detection. I'm trying to think of ways to avoid integrating external peripherals that aren't part of the phone.