i-Prompt is an app I picked up from the ASD iPod Touch Project Apps (.pdf) and have tested it out. It is a free app developed by iPrompter, a company that produces professional teleprompt devices.
Since the software is originally for teleprompting, this is an example of technology created for one purpose being used in a similar way as assistive technology.
i-Prompt works for both iPad and iPod Touch. I think that it can be used both by parents, teachers and caregivers to prompt those developing independence with the next steps of a task as well as by more independent individuals to remember steps in a task. This means that it can be useful for people who have a hard time remembering instructions, and to overcome stressful and confusing situations when something unexpected happens.
To test it out, I wrote my own prompt script, and tried out some of the features. It can be set up to scroll through the script at a set pace, but can be paused and manually scrolled through via touch screen. The font can also be adjusted to different sizes, font type, and the colours. I found it very easy to use. The only downside that I can find is that it's text-based and so requires the ability to read and follow written instructions. Which means that it's a good in-step tool for independence, but is not appropriate for those who need images.