According to Apple's product page, the Airport Extreme…
"…can turn your external USB hard drive into a secure drive you can share across your Wi‑Fi network and access securely over the Internet."
My interpretation of the "access securely over the Internet" part is that if I plug in an external hard drive to an Airport Extreme on my home network, I can get to it from anywhere via the internet… including outside of my home network.
Am I interpreting this correctly? If so, it sounds like a pretty awesome feature! I guess I'm skeptical though because when I Google around for this, I find nothing relevant… including any info from Apple. What gives?
Best Answer
Sometimes, the only way to get an answer is to try it for yourself! So, I went out and bought an Airport Extreme. Bottom line:
YES, YOU CAN ACCESS AN ATTACHED DISK REMOTELY FROM OVER THE INTERNET!
The magic happens with iCloud's Back to My Mac feature. Here's how you do it:
Now, when you're away from your local network, just click the name of your AirPort Extreme in a Finder window's sidebar (if you don't see it, make sure "Back to My Mac" is ticked in Finder > Preferences > Sidebar).
Amazingly, that's it. It blows my mind that Apple isn't promoting this more heavily or that there's little talk about it out there. To me, this is a pretty killer feature!