Nokia PC Phone is an extension for the Mozilla Firefox browser that you can use to perform various tasks on your phone directly from your web browser, and you won't need a new user interface to do it.
It has an SMS message manager to send text messages directly from your computer. Similarly, it includes a calling system to enable you to conduct a phone call from the same interface. And if that weren't enough, it also has a contact manager you can use to edit the details in your address book.
All of this makes Nokia PC Phone a really interesting extension.