Wearable device for coupling to a user, and measuring and monitoring user activity

A system for measuring an angle of a joint of a user, comprising:

• a center hub;
• a first arm including a first outer end and a first inner end and configured for attachment to a first limb portion of the user at the first outer end and to the center hub at the first inner end;
• and
• a second arm including a second outer end and a second inner end and configured for attachment to a second limb portion of the user at the second outer end and to the center hub at the second inner end,
• wherein the first arm defines a major axis between the center hub and the first outer end, and
• wherein the first arm further includes a pivot configured to facilitate the first outer end to be rotatable relative to the center hub and about an axis parallel to the major axis.