The ability to sync and carry on text message conversations regardless of whether you’re using an iPhone, iPad, or Mac has always been one of the slicker features of iMessage, but until recently, there always seemed to be a disconnect between doing this with actual iMessages as opposed to traditional SMS text messages. Since not all of us have friends who exclusively use Apple devices, it was always a bit of a juggling act to figure out which ones you could message from your Mac or iPad and which friends made you have to reach for your iPhone to communicate. Fortunately, iOS 8.1 introduced the welcome feature of bridging this gap with “SMS Continuity,” which allows SMS and MMS messages to be sent and received using any device registered to your Apple ID. The options to control this can be found by going into your the Settings app on your iPhone, and selecting Messages, Text Message Forwarding. Here you’ll see a list of all of the non-iPhone devices associated with your Apple ID, and you can simply toggle the option on or off for the devices you wish to have participate in your SMS conversations.
As a security precaution, toggling a device ON will display a numeric code on the remote device that you’ll need to enter into your iPhone to confirm the pairing.
Once you’ve done that, the feature should just start working in much the same way as it always has for iMessage. Unlike iMessage, you’ll still need your iPhone to act as the gateway for SMS/MMS messages, as it’s responsible for transferring the messages between your other devices and your cellular carrier’s network. This is done wirelessly over the Internet via iCloud, however, so as long as your iPhone is on and has an Internet connection, the feature will work regardless of whether your iPhone is in actual proximity to your Mac, iPad, or iPod touch.