Via that Sony Ericsson T610 for Mac OS X page I mentioned the other day: PhoneAgent is an OS X app to manage resources on your SE phone, including a phone book editor, direct access to SMS and MMS messaging from your Mac, a theme editor, and more. $29.95 is a little much for a toy for my toy, but I otherwise haven't figured out how to do some of these things easily with the default facilities.

Salling Clicker and Romeo are both apps to let you control Mac OS X applications via your Bluetooth-enabled phone as a remote control.