  We describe Hydroprompt, a prototype for sensing and motivating healthy water
intake in work environments. In a 3-week field deployment of Hydroprompt, we
evaluate the effectiveness of three approaches to behavior change: historical
information enabling users to compare their water intake lev- els across
different times of day and days of week, implicit feedback providing subtle
cues to users on the current hydration levels, and explicit prompting at-
tempting to remind participants when hydration falls below acceptable levels or
when substantial amount of time has elapsed since the last sip.
