For most devices using the Android software when you see the keyboard pop up you can use text to speech capability. For some devices you may first have to enable this in the settings from the main display.

When the keyboard pops up look for a key that looks like a microphone. You may also be able to set your device up for specific commands. Such as, search, open web browser, open a specific app.

You will have to decide what the command should do and the set it up with a command phrase. I will check specifics and repost.