In May we reported about a 17 year old student who conducted a study on the effect of iPods on pacemaker at the Thoracic and Cardiovascular Institute at Michigan State University.

Now researchers at the Children’s Hospital in Boston, Massachusetts, will start an extensive test on how four different MP3 players affect children and adult patients with pacemakers.
The first study showed electrical interference in 50% of the cases when the iPod was held just 2 inches from the patient's chest for 5 to 10 seconds.
More details on the Telegraph.