This Slack bot gives users the ability to silently interact with Alexa using the same commands they would speak out loud. It allows users to communicate when the room is noisy, or when voice communication isn't appropriate. Not all commands are available, but it is a neat alternative to using the smartphone app.
https://www.notebookcheck.net/Silent-Echo-uses-slack-to-allow-text-communication-with-Amazon-Alexa.236918.0.html