The Amazon Alexa voice assistant is great, and even allows you to create a shortcut on your launcher screen, but there isn't an easy way to chain it to IFTTT or Bixby Button Remapper-type apps... until now!
Now any app that can launch an Android application can launch the Alexa voice assistant. (Requires installation of Amazon Alexa app)
Note: This app does not support launching by voice command. You must launch it by tapping the icon in your launcher or from a utility application like IFTTT or Bixby Button Remapper.