Magnetic devices and implantation methods are provided for use in the treatment of obstructive sleep apnea. The devices include a sheet-like element having ferromagnetic qualities. The device may also include a permanent magnet attached to the sheet-like element by magnetic forces. The devices are implanted in soft tissue surrounding the airway and in tissue space beneath the pharyngeal wall to exert forces on and/or change the shape of the soft tissue. The magnetic devices may also include a bladder containing a magnetorheological fluid that stiffens soft tissue when exposed to a magnetic field.