Guidelines/Best practices/Studies for smart mirror interactions?

A lot of the questions on UX StackExchange refer to UI design for Mobile/Desktop applications. My question deals with UX for smart-mirrors so I hope it will be relevant.

The smart-home is more popular than ever and I have seen mirror prototypes and tutorials to create smart-mirrors. I have gotten interested in this object. I was wondering if there are already any recommendations, guidelines or study existing. I am wondering about the best way(s) to interact with a mirror, such as:

  • Turn on and off a mirror: proximity captor/physical button/etc.
  • to switch/recognize user profiles: while I was thinking about face recognition, I realized privacy could be a problem.
  • Global interaction with the mirror itself: gestures, voice?

I have seen some examples that are to me illustrating a bad User Experience:

  • I had a look at this project http://www.rafaeldymek.com/portfolio/apple-mirror/ and the mirror interaction is tactile. I believe the end-user would not like to have fingerprints on the mirror.
  • Another example is a mirror available on the market. The user interacts with a mini keyboard + trackpad device.