[deelowe]

Many electronics work that way. Motors can also generate electricity. Inductors can create or sense magnetic fields. Resistance is generally temperature dependent. Etc.

[parenthesis]

You can use headphones as a microphone, or a (dynamic) microphone as a loudspeaker.

[______-_-______]

This is my favorite one. Being on stage and hearing music come out of your mic is a hell of a trip.

[petschge]

Everything is as temperature sensor. Some elements also measure other signals.

[user_7832]

Just made be realize, when you cook, the food is basically a temperature sensor. (Burnt) Toast is a great example.

[jbay808]

Almost any high-efficiency energy transformation is reversible, in fact!

[amelius]

I just hope my TV can't be used as a camera ...

[drdeca]

Well, pairing the TV with a light sensor in a fixed location, and like, having the tv alternate between a sequence of different patterns, and recording how this changes the reading of the light sensor, and assuming that the room is otherwise dark, uh, apparently can be used to produce an image of the room as if taken from the location of the tv and illuminated from the position of the light sensor?

[amelius]

Ok. Most TVs are equipped with an IR sensor, so with a slightly more capable one you could take an image from the pov of the TV, and illuminated from the TV. Yikes.