Twitter’s first developer conference in four years, Flight, is in full swing and we’re already seeing some announcements out of San Francisco. Perhaps one of the most interesting is Digits, Twitter’s plan to replace the password with a user’s mobile phone number. Here’s how it works.

When logging into a service, users will be presented with the option to log in via their mobile device. If that route is selected, the user will enter in their phone number and receive an SMS-based confirmation code. That code is then entered into the app to gain access.

Digits would effectively eliminate the need of having to remember a username and password as well as having to deal with CAPTCHAs. What’s more, it could result in a safer overall environment when you consider people often use the same password for multiple services and the strength of said passwords are sometimes comical at best.

It’s worth clarifying that Digits isn’t part of Twitter. Rather, it’s a product that developers can build into their own apps to facilitate logging in.

The idea for Digits came about last year when Twitter senior product manager Michael Ducker was touring different areas of the world as part of a user research project. It became apparent that much of the problem with signing up new users was related to having to own an e-mail address.

By that, I mean that many people outside of the US don’t have an e-mail address. Instead, they identify through their cell phones.

Would you feel comfortable doing away with usernames and passwords in favor of giving out your mobile number? Let us know what you think in the comments section below.