1Password doesn't quite meet all of the criteria for anywhere, anytime, any platform access to your password data. However, it's a breeze to use and a good choice if you're in a Mac-centric household.
It will also work if you just need to synchronize passwords with a Windows machine at work and an iPhone from the road. It supports the iPhone, iPad, iPod Touch, Palm and Android phones. But if you want access from your BlackBerry or from a Linux computer, or if you want a version that runs from a USB key, look elsewhere.
To back up and synchronize your data you'll need to set up an account with storage-as-a-service vendor Dropbox. (You can get up to 2GB of storage for free, which should be plenty for password data). Dropbox creates a folder on each computer and then synchronizes among them. Configuring 1Password to work with Dropbox is easy: You simply move your 1Password database to your local Dropbox folder.
Technically you can view your password data directly on the Dropbox Web site using a browser, but it's not an obvious process. You have to go to Dropbox, log into your account, click on the "Files" tab, and click on the 1Password.agilekeychain file, which exposes the 1Password.html file. Clicking on that brings up the 1Password "Unlock" screen so you can decrypt the file and view your password data. Because you must log into Dropbox first, you can't just create a browser bookmark to go directly to your 1Password data.
The Mac version of 1Password includes a standalone application to manage your data and a browser extension that provides access to your passwords by way of either an embedded "1P" button on the navigation tool bar or controls on a 1Password toolbar. The toolbar includes a context-sensitive shortcut button that determines what site you're currently visiting and suggests the appropriate account credentials when clicked.
On the Mac, iPad and iPhone versions, 1Password has easily the prettiest user interface in the group, and it's simple to use as well. 1Password integrates with several popular Mac browsers.
The versions for the iPhone and iPad include an integrated browser. Both automatically fill in credentials but don't automatically submit them to the site. You can also copy and paste credentials into a Safari window.
One irritation on the iPad: Switch away from 1Password by clicking the iPad's Home button and you're logged out (RoboForm performed the same way). LastPass did preserve my sessions on the iPad until they timed out, regardless of how many times I switched away. The developer says it will support multitasking with Apple's release of iOS 4.2 in November, so you won't get logged out every time you press the home button.
The Windows version, still in beta, provides the same basic functions, although the pop-up user interface for Windows browsers (Firefox or Internet Explorer only) has a different look and feel. And unlike the Mac version, in Windows you need to use the browser add-on to log into Web sites. You click the 1P icon to bring up the dialog box, click the "Go and Fill Login" button, and then pick the site from a list. The pop-up dialog fills in credentials but doesn't automatically submit them unless you have checked the "Auto-Submit Logins" box (it is turned off by default).
Agile Software licenses 1Password by the user rather than the device, but you do need a license for each platform. The license for the Mac version costs $39.95. The Windows version currently costs $19.95 while it's in beta; on release, it will also cost $39.95. You'll pay $9.95 for the iPad, iPhone or iPod Touch -- a $14.95 Pro version lets you install 1Password on all three iOS devices.