Singing, or playing a musical instrument, requires fine muscular control.

ECONOMIST: The biology of music | The

The myTREK's comfortable arm-strap design fits over the muscular portion of the user's forearm and provides convenient track and volume control.

ENGADGET: Scosche myTrek sends workout vitals to your iPhone, starts shipping now for $130 (video)

Arya had spinal muscular atrophy, or SMA, a progressive and fatal disease in which the nerves that control the muscles slowly waste away.

FORBES: For Arya