Again, the mechanisms, though quite simple. Here I will teach You how to make a hidden chest in the wall in Minecraft PE.
Let's start with the walls, I built a rough imitation of the walls of the house:
We will build on the other side of the wall. Let's start with the pistons and the input signal thereto:
Input signal thereto:
Set the chest and brings red dust to the desired location in the wall:
Install the lever and check:
Everything works. I think the arm is too noticeable. For this, I as decor set of buttons on the wall, only one of which activates the mechanism:
But in this case, the mechanism is activated only for a short time to time to open the chest.