Echo devices are designed to detect only your chosen wake word (Amazon, Alexa, Computer, or Echo). The device detects wake word by identifying acoustic patterns that match the wake word. Once the word is detected, audio begins streaming to the cloud, including a fraction of a second of audio before the wake word. No audio is stored or sent to the cloud unless the device detects the wake word (or Alexa is activated by pressing a button).
WiFi and Any device like Android, pc, mac, and tablet etc. that downloads apps for the free Amazon Alexa app. You don’t need Prime unless you want to listen to Prime
You can do all main music apps free through the Alexa app, so unless you want to shop via the echo Dot, nothing but free Alexa app and WiFi is the minimum needed.
Download Alexa App / Alexa.amazon.com / Amazon Alexa App / Amazon Alexa Login