Computers:

I used my MacBook, it worked fine, except the computer graphics were a little off. Also if I open a computer game in a lucid dream I usually get sucked into it.

Televisions:

I watched TV before, worked like it would IRL.

Mirrors:

They work fine for me. Mirrors have been kind to me, ever since I pulled one off the wall and ate it. However if you expect a scary image you'll get one.

Light Switches:

My father used to have dreams were there would be an evil ghost in the house at night and the light switches wouldn't work. Personally I've never used light switches in dreams.