Hey online21;
There is a long thread debating the octopus (or safe second)
here. It's a doozie!
Now, I would chose an octopus or what I now know as a backup, that I would not mind breathing from myself. Now, there are different thoughts on this and how it can be or should be done. As an example, I practice to give the regulator that I am breathing from my mouth and I switch to a backup. This alleviates the question, am I giving a regulator that may or may not work to an already panicked diver?" Also, I know my backup works as I checked it before the dive (ALWAYS) and it is as close to my mouth without being in my mouth, hangin' around for the ride but ready for immediate service. BTW I have and use Apeks ATX200/ATX50 (Primary/Backup) and ATX100/ATX50 (Primary/Backup) and in both instances you see I breathe the ATX50 in the OOG scenario when I am donating. That's what I started with owning (ATX50/ATX40) and the ATX50 is a great regulator for anyone (well for anyone with Apeks tastes).
But again, there are many ways. If you decide to use the triangle method of alternate stowage (as in it will be located anywhere between your chin and the lower portions of your ribcage), choose an octopus that breathes easily, has a long hose (38-40 inches) and can be stowed easily and more importantly accessed easily! You do not want to induce more panic to an OOG diver by making him guess where his next breath is, or by giving him a poorly breathing regulator, or by having him/her fight to get the mouthpiece out of the scumball holder or cinched bungee loop you might use. And no regulator should be stowed in a pocket (out of view and nearly impossible to immediately deploy)!
I would shy away from the inflator/alternate system or integrated solutions as well. The inflator hose is typically too short for you (as you keep that one and donate your primary regulator) especially if you want to turn your head to the right, and the hose that is on your primary may be too short to adequately donate unless you have made provisions when you set your gear up.
And finally, no matter what solution you choose, make sure you practice the skill of deploying your equipment. It does no good if, in an emergency, both the OOG diver and you panic because of mis-communication or you just don't know what to do. Practice makes better.
Good luck and I hope this helps.
With kind regards,
Thomas