You can use this app to control your DirecTV box from your smartphone.
Notice that this is not the official DirecTV Box app, but you can control it with this app.

In our app, we have several remotes models, so you can choose the remote that's right for you.

The app helps you operate your DirecTV Box device even if you cannot find your remote control! But, please note that it requires your phone to have an IR sensor.