That usually doesn't look very nice, especially when you start to type letters (does anyone really like this transparency effect in karmic, when you hover over a desktop notification?). But yes, can be easily done.

I am surprised you find the look of this appealing, because my blurring effect looks like sh^W it could be improved

Also, the plan for this message bar is to have a nice send button and this smiley chooser you know from the conversations app.