The two most common forms of providing assessment feedback to students have been written comments on the assignment or face to face discussions. However research reveals that written comments are often limited in depth and marred by ambiguity while face to face discussions are often impractical and dependent on student memory. In contrast over recent years we have witnessed an increase in technology enhanced modes of feedback delivery. At its simplest this involves annotating documents with written comments. However, there are a variety of other options. This paper will outline the limited but growing empirical research on the design and impact of video, audio, screencast and other annotation feedback mechanisms. Drawing on this literature and the presenters' own research we propose a series of design principles for the creation of effective technology enhanced feedback.