Clocks send a Redstone signal when it turns day/night time.

So when clocks are put on an item frame (or Mojang possibly makes the clock a block in 2d form), they will conduct electricity, and power any Redstone object or Redstone near it. This could help with pearl clocks that teleport you home when it turns night time, for example when it turns night time and the clock shows that, it will send a Redstone signal through the Redstone behind the block the clock and item frame is on, and power a piston that will push the slime block the ender pearl was bouncing on, causing the player to teleport to the location they set it to teleport them to.

(edit: for java)