Master Password is a revolution in password management.
It aims to secure your online (and offline!) life by changing the way you deal with passwords.
You already know the problem:
Passwords are confidential information between you and a site. They should never be shared with anyone else, definitely not other sites. Yet that's exactly what happens with most of us: Hundereds of online accounts to manage and authenticate, we can't help but reuse one, two or five passwords that we can remember. Maybe we keep a paper stuck to our monitor with a list of passwords on them, because we realize the truth:
It is impossible to remember a secure password for each of our accounts and still keep those passwords both exclusive and confidential.
Multiple solutions exist:
Sites that realize that passwords aren't the end-all of authentication usually implement some sort of alternative authentication mechanism: OpenID, SAML, some form of mobile authentication, secure tokens, etc.
The problem here is that these solutions only work for the select few sites that have chosen to implement them; and then you, the user, are stuck with whatever mechanism the site has chosen for you.
To solve the problem for other sites, there are programs that remember our passwords for us.
The problem with these is that they do not actually help us with setting exclusive and confidential passwords for our accounts. They just offload the work of remembering passwords, and at a great expense: If you lose your data, you lose your online identity and are locked out of everything.
Master Password aims to turn the tables in favor of the user, you.
In the end, what we really want is a way of dealing with passwords in an exclusive and confidential way without having to remember them, and without running the risk of losing our online identity to fraudsters.
Master Password does exactly this. You remember a single master password. Make it a long and secure one. Master Password uses this password along with the name of the site that you want to log into and generates a secure but unique password for that site. What's more, it doesn't store this information anywhere. If you lose your phone, the thieves can get none the wiser from it. You kick yourself for losing your phone, pick up any other phone, start the application, enter your master password, and instantly have access to all your passwords again. No sync, no backups, no hassle.
Master Password is available from Apple's App Store for iOS and Mac. The Mac application currently requires the iOS application and iCloud to be enabled and set up on both the iPhone and the Mac.
The application is fully open source under the GPLv3, which means you can inspect the code and build the application for yourself, if you prefer. You can find the Master Password source code on GitHub.