From Amazon's help pages:
Your Amazon Echo updates automatically when it's plugged in, idle, and connected to Wi-Fi.
In addition to bug fixes, the latest software version for Amazon Echo (2249) includes new and enhanced features:
Use hands-free voice control for paired devices
After you pair a mobile device (such as a phone, tablet, or laptop) with Amazon Echo, you can use hands-free voice control to listen to music, audiobooks, and more from that device on your Amazon Echo. To learn more, go to Use Hands-Free Voice Control for Paired Devices.
Additional voice commands for Shopping and To-do Lists
You can now review items on your Shopping and To-do Lists with your voice. To learn more, go to Manage Your Shopping & To-do Lists.
Play "Simon Says"
You can say "Alexa, Simon says" to have Amazon Echo repeat whatever you have in mind.
To determine the current software version for Amazon Echo:
Open the Amazon Echo App.
Open the left navigation panel, and then select Settings.
Select your device, and then scroll down until you see Echo software version.