It should work on any iOS 8.1 device.
This is what Apple says,
"To use Continuity for SMS and MMS on your iPad, iPod touch, and Mac:
Update your iPhone to iOS 8.1 (when available).
Enable iMessage on your Mac and iOS devices.
On your iPhone, go to Settings > Messages and turn on Text Message Forwarding.
Your iPad, iPod touch, or Mac will display a code you can enter on your iPhone to verify the SMS and MMS feature."