What precautions should people with electronic implants (like pacemakers) take with the mTwisT dial?

People wearing electronic implants such as a pacemaker or insulin pump should not carry the mTwisT control knob in their pockets, as it is highly magnetic and may affect some implants. Persons with electronic implants should keep the control knob at least four inches away from the implant at all times. (Page 2)