Adam Pash at Lifehacker has put out this complete guide to Simplenote, but even that feels like more explanation than it needs. In short, it comes down to two words: Just. Type.
Simplenote, for the uninitiated, is a web and iOS application that automatically stores all of your plain text and syncs it between your connected devices. Say for instance, you start writing something in the Simplenote web app on your computer. You leave to go run some errands, but before you do, you sync your iOS device (which could be an iPad, iPhone and iPod Touch) with Simplenote. While you’re out, you’re struck by inspiration and decide to continue writing.
But what if your 3G service suddenly goes down? Not a problem, because the Simplenote mobile app saves all your work. The next time you’re in reach of a data connection (cell or wifi), you can sync again. Since it’s all text, syncing is incredibly fast, so there’s no sitting and waiting while your files upload. Best of all, the iOS app and the webapp are free (though there is a “premium” option that disables ads and provides a few other features for $8.99 a year).
More than any other app, it’s the one that I think has actually made significant change in my life. Any spare moment is now a potentially productive one, and for some tasks (like grocery shopping), Simplenote feels like an extension for my brain.