combobox TV type

I’d like to replicate "Combobox" functionality with a TV- you can either choose a value from a dropdown select box, or type a value in manually; and if you type the value in it’s added to the select box next time.

The best solution I can think of is to use the @SELECT binding and a separate module to add values. Which isn’t as user friendly as I’d like.
How are other people dealing with this situation?

That’d be a great one to add indeed. Some good example code floats around too, particularly with extJS.