A block that acts as a receiver for whispered chat text to it. And you can set it up with a list of words that can act as password "Voice Commands" in a multiplayer environment.
Example) Walk up to a Volume sensor, The Voice Receiver Block wakes up and listens for any of the keywords you have Assigned Via a Sequencer logic block. And if the right password is said it opens the door. If not, a timer counts down if the player doesn't leave the Volume Sensor, then an alarm is triggered sending a whisper to a "Comms Link" to the player that owns that system.