IT’S been true for a while that if you need to transcribe an audio recording, find contact information for a company, summarize an article, or perform any number of routine tasks, an anonymous online worker can do the job for a small payment. Amazon’s Mechanical Turk, for example, recently listed 230,000 available microtasks.

These services have a drawback, however: the work is not done in real time. Workers pick up the tasks that interest them and for which they are qualified, but as independent contractors they work on their own schedules.

Computer science researchers have been trying to build systems that summon online workers on demand and produce immediate results. Much initial work has focused on completing tasks for people with disabilities, because that is where the need is great. For example, a blind person may need to identify the contents of a can from a kitchen cupboard right now, not later. A deaf college student may want to follow the give-and-take of a seminar discussion as it unfolds in the classroom, and not wait to read a transcript the next day.

VizWiz, a free iPhone app developed by Jeffrey P. Bigham of the University of Rochester and colleagues in its Human Computer Interaction program, gives real-time help to blind users.