Technology found in Google Pixel and Pixel XL suggests that smart flip cases are coming for the pair
Thus far, there are no third party Pixel cases designed to take advantage of the technology. However, if you place a magnet near the "G" logo on the back of a Pixel or Pixel XL phone, or on the corresponding area on the front of the phone, the handset will awaken. It won't turn off the display because removing the magnetic field from the area will also turn on the screen.
We wouldn't be surprised to find out that case manufacturers plan on adding magnets to their Pixel and Pixel XL cases. After all, it is a cheap way to add more functionality to an accessory that many Pixel and Pixel XL buyers are going to purchase to protect their investment.