Amazon shows you how to make an Echo with Raspberry Pi

You’ll need to snag a Raspberry Pi 2 and a USB microphone to make it happen, but you’ve probably got the other required hardware (a micro-SD card for storage, for example) lying around. Unfortunately, due to limitations with Amazon’s Voice Services, your creation can’t listen for trigger words like Echo and Echo Dot. Instead, you’ll have to hit a button to issue commands. – Divindra Hardawar, Engadget