The combined presentation of linguistic information in the form of speech and handwriting has long been known to be effective by movie directors. Typically, a letter is shown on the screen, and an off-screen voice reads it aloud. The ambiguity in the handwriting style is reduced by the spoken words, and vice versa.
Issues here are the optional synchronization of handwriting and speech presentation. Modes are: (i) completely asynchronous, the handwriting can be displayed almost immediately, and is continually present on screen while the speech production takes its time; (ii) synchronous, incremental, where the handwritten words follow the spoken words; and (ii) synchronous, by highlighting the 'current word' in the handwritten ink on screen. These paradigms are relatively well known for the case of speech synthesis and machine-printed fonts on the screen.