Your password can be different than the iPhone database you sync with, and you can sync between multiple devices.
Firebox uses best-practices encryption, with CBC-mode Blowfish encryption and PBKDF2 strengthened keys.
Edit the sample database to your liking, or define your own.
Firebox iPhone is not required to use Firebox Desktop. It does let you take your information safely along with you, however, and safeguards it if you should lose your phone.
Currently, Firebox Desktop lacks some of the newest features Firebox iPhone has, but it is under active development, and will be at feature parity soon.