Workrave[1] and antirsi[2] have helped me take breaks like this regularly. Beyond the wrist relief it's nice to take a short break and refresh my mind before continuing work.
[1]http://www.workrave.org/ [2]http://tech.inhelsinki.nl/antirsi/
[1]http://www.workrave.org/ [2]http://tech.inhelsinki.nl/antirsi/
There is a work method based on this as well: http://www.pomodorotechnique.com/