A free app for Android, by SPB Infotech.

Command Block for MCPE is a mod for Minecraft Pocket Edition (MCPE). It lets you use chat commands in multiplayer servers and local servers, using a Redstone power source. It will let you do things like activate a specific command that otherwise you wouldn’t be able to do through chats.

How do I install it?

The first thing you need to do is to download the file you want to install. For that, you need to go to the Downloads tab of your device’s file manager. Next, you need to open the file you just downloaded and start the installation. After the installation is complete, you need to start Minecraft. If you are on a server, you will need to select the server you want to join.