Remotely accessing files on one Mac from another has been possible for years, but now a Mac version of the iTwin (US$99) device is intended to make it easier to securely send files back and forth over the Internet. After giving the device a try, I found it to be much more confusing than just using something like Dropbox for file sharing, as well as being poorly implemented on the Mac. Read on for a description of how it works, along with my take on why the iTwin might not be the sharing solution you want to use.
Using iTwin for Mac
The iTwin for Mac looks like a double-ended USB flash drive that pulls apart in the middle. It doesn't actually have any onboard storage; instead, it uses the Mac (or PC -- it's cross-platform) on the other side of an Internet connection as storage. Have a 2 TB drive sitting in that iMac at home with plenty of free space, and want to use it as storage for your MacBook Air while you're on vacation? No problem, as long as you have an Internet connection available.
To install the iTwin's software, you simply plug it into an open USB port. A DVD image appears on your Desktop, you open it and click "LaunchiTwinMac" to install. This is a bit more than the "automatic install" that iTwin promises, and the installation leaves a folder in your Applications folder filled with a bunch of detritus (see below) one would normally associate with a Windows application. There's also a iTwin preference pane installed in System Preferences; basically, it allows you to uninstall the iTwin software from your Mac.
There were no more instructions about what to do, either in the installation notes or on the iTwin website. I simply unplugged the iTwin (it never squawked at me about not dismounting it first), and then plugged it back in. The second time, I was asked to give my iTwin a "friendly name" to identify it and also to provide an email address for a disable code. This disable code allows you to disable one half of the iTwin pair should you accidentally lose the other, thus keeping unfriendly eyes away from your digital stuff. At the same time, unique encryption keys are created for both halves of the device, ensuring that the only way you can get access to your Macs is by having your hands on both USB dongles.
At this point, an empty folder called "Steve's iTwins Local Files" appeared on my desktop and a tiny green icon appeared in my menu bar. I figured it was about time to pull off one half of the iTwin pair and plug it into my MacBook Air.
After going through the iTwin software installation process on the MacBook Air, I was greeted with a second icon on my desktop, this one called "Steve's iTwins Remote Files". I decided that I would use that to transfer a photo to my iMac, so I dropped a file on it. Instead of putting the file into a specific folder on my iMac, it put it onto the desktop and also put a copy into the Local Files folder. That got a big "huh?" (actually more of a "WTF?") from me.
It turns out that if I drop something into the "Local Files" folder on one machine, it appears in the "Remote Files" folder on the other computer (and vice-versa) and I don't end up with files and folders spewed all over the other machine's desktop. Whew.
Let's face it; I'm used to Dropbox, where I have one folder on each device that is identical. Anything that goes into that folder shows up on every device. Here, there's a (to me) confusing mix of "local" and "remote" folders, as well as a DVD icon that never disappears. To get those off of my desktop, I changed my Finder preferences to hide external disks, CDs, and DVDs.
What's the benefit of using the iTwin? I'm guessing that it would be security more than anything. To quote the marketing talk on the iTwin site, "No configuration, no VPN token card, no login. With AES-256 hardware-enabled encryption. It's as secure and simple as data transfer gets." If you happen to lose one half of the iTwin pair, you can disable access.
When you want to share large quantities of information, say your entire Pictures folder or a huge Documents folder, you drag that folder icon over to your Local Files folder and drop it. Rather than actually duplicating the folder, that process appears to just enable an alias pointing to the "real" folder. To stop sharing, you just drag that folder out of the Local Files folder.
For doing backups, things get a little strange. With Dropbox, if I want to back up a complete folder, I can drag that folder to my Dropbox folder and it's going to be synced with Dropbox's server and then to every Mac or PC that I have Dropbox on. While iTwin does a wonderful job of sharing in real time, the only way I can truly back something up is to drag it to the Remote Files folder and let it be copied. That can take a while depending on the size of the folder (the same is true of Dropbox), but iTwin insists on placing that copied file onto the desktop of the remote Mac.
While the security of the iTwin device might make it attractive to some Mac owners, I found it to be very awkward in its implementation and quite "PC-like." Frankly, I prefer the ubiquity of Dropbox, which uses SSL and AES-256 encryption both for transferring and storing your data. Rather than having to worry about losing a USB dongle with iTwin, I just boot up my machine and there's Dropbox waiting for me. No software on a remote machine? I can log in from any web browser -- whether it's running OS X, Windows, or any flavor of Linux -- and get to my Dropbox data. And with Dropbox, I can also get to my data from my iOS devices; with the iTwin, they're left out in the cold.
If the iTwin did something really spectacular and different, like providing an immediate way to control my remote Mac (like Back To My Mac is meant to do), then it might be worth the time and money.
The iTwin sounded like a good idea, which is why I agreed to review it. Unless I'm really missing the point of this product (and please let me know in the comments if there's something that I just don't seem to be understanding), I can't see any reason to recommend it.