Developer: Callpod Inc.
Price: free Download on the App Store
Common sense should tell you that it's risky storing highly sensitive data such as login IDs and credit card numbers on your iPhone or iPod touch, but if you insist, the best option I've found thus far is Callpod's Keeper.
Keeper is a database for info that you need to keep to yourself. It's simple to use and works effectively.
Setup is easy. Launch Keeper and enter a password. A solid password is one that is 6 or more digits long with a mix of alphanumeric and other characters. If you're forgetful like me, use a "passphrase," that's easy to remember. For example, you might use something like "Ta50WtLYL!" Translation: "There are 50 Ways to Leave Your Lover!"
Next, tap the + in the upper left corner and start entering your data into the fields provided. Say, it's: Sears Mastercard, Name on the Account, Credit Card Number and Notes, if needed. Save, and that's pretty much it. Sears Master Card will appear on your All Records list, which is sorted alphabetically. Tap the Recent icon on the bottom of the screen to see your latest entries.
If you have a long list of items, you can do a search from the bar at the top of the screen.
What matters most with an app like this are its security features beyond merely creating a password. Options for security, FTP export/import and for configuring field names and headers, are all accessible from the Options icon on the menu bar.
Keeper's security options are to enable/disable encryption, self-destruct mode and password reset. This app uses 128-bit encryption to encrypt your data, which is about as good as it gets short of something a spy agency might use. It would take significant amount of computing power and several years to crack it.
As an additional layer of security, Keeper has a self-destruct feature that will wipe all your data after five unsuccessful attempts to enter your password. That's not likely to be a problem for you--at least not, if you've backed up your data.
To backup, you have two options: The first is to back it up to your desktop using iTunes. The second is to export it via FTP to a server. I tried encrypted export and import and it worked without a hitch. Your data is never stored on one of Callpod's servers, which is how it should be.
In its FAQ, Callpod says it plans to release desktop widgets for Mac OS and Windows so less-sophisticated users won't need to learn how to use an FTP client.
As for the FAQ, it explains well what you need to know about using Keeper and that's where you should start first.