In one aspect of the disclosed implementations, a device includes one or more motion sensors for sensing motion of the device and providing activity data indicative of the sensed motion. The device also includes one or more processors for monitoring the activity data, and receiving or generating annotation data for annotating the activity data with one or more markers or indicators to define one or more characteristics of an activity session. The device also includes one or more feedback devices for providing feedback, a notice, or an indication to a user based on the monitoring. The device further includes a portable housing that encloses at least portions of the motion sensors, the processors and the feedback devices.