So not sure if this has been posted before. I have setup an old nexus phone as an always listening alexa device in my office and it also runs smarttiles and lannouncer. I used the following app for alexa and always listening:
Note: I am in no way associated with the app developer
Alexa Listens: https://play.google.com/store/apps/details?id=com.willblaschko.android.alexalistens&hl=en
Also I changed my trigger phrase to “Hey Jarvis”.