From MP3Car.com Wiki

[edit] General Features & Abilities

• View the phone book from your cellular phone
• Dial numbers from the phone book
• Dial numbers manually
• Send, receive and read SMS/MMS
• Notification on incoming calls
• Phone battery & signal strength indicators
• View "Missed calls", "Received calls", and "Dialed calls" phone books
• Remote Control: control other applications on your PC from your mobile phone
• Use your mobile phone as a Multi-Tap input device.

[edit] Software

• PhoneControl.NET (broken link)
• FreeFone
• RRMobile

[edit] Connectivity

• Bluetooth
• IrDA
• USB
• Serial