I have a iPhone 6, 2012 rMBP 15", iPad 2, and 2007 iMac. They are all on Yosemite and iOS 8.1.3 I was able to get SMS relay working on both my rMBP and my iPad. If I went into Text messaging forwarding settings on the phone, only those two devices show up by not my iMac. I know it works and I have had it working before, however I just recently restored my mac because I put a SSD in it. Now I can't get my relay working on my iMac. It's not that I am not getting the code, but the options to even turn on SMS relay isn't showing up for my iMac. Any suggestions? I have tried turning iMessage on and off, on both the computer and the phone. I have tried logging out and logging back into iCloud. I have tried everything within reason. It may also be worth nothing that phone calls are working on both my iPad and Macbook but not the iMac Any suggestions?