There is no way to type text using the keyboard in Austin. However, there are a couple of very crude work arounds...
(1) One could type in Paint, and copy-paste the text as an image unto the Austin page.
(2) Austin has a pre-defined set of strokes that resemble the alphabet. Those are used for stress testing (see the *automation* files).
With some work, one could re-target the keyboard to pick those pre-defined strokes and place them on the page. Of course, the user will have to implement the text box logic...
The pre-defined set of strokes are created by having somebody write down the strokes using Austin, and then Austin can dump the data to the debug window for later use.
(3) One could add the XAML textbox control to receive the input, and then render it using the predefined strokes... [that would be the easiest]