For my Assistive Technology class last semester we had to come up with an idea for an assistive tech device for a student. I chose to create a prototype for a student with Pervasive Development Disorder (PDD). Autism and Asperger's Syndrome are two of the most well-known forms of PDD.
This particular student does not respond well to transitions. To my knowledge, his team of instructors at school do not give multiple notifications of the upcoming activity. I suggested that we use a clock that counts down the time of the current activity. If he can 'see' that time is decreasing on his current activity while at the same time someone is verbalizing the countdown AND providing deep pressure on his shoulder or arm to get his attention, he may be more receptive to ending that activity and starting a new one.
In the real world this would probably be laminated or created using a computer or something but you get my drift. Some of my classmates actually created their assistive technology and gave it to the students, who were elated, of course.