Miyuki Shiraishi Yasuyuki Washio Chihiro Takayama Vili Lehdonvirta Hiroaki Kimura Tatsuo Nakajima Tracking behavior in persuasive apps: is sensor-based detection always better than user self-reporting? 4045-4050 2009 CHI Extended Abstracts http://doi.acm.org/10.1145/1520340.1520615 conf/chi/2009a db/conf/chi/chi2009a.html#ShiraishiWTLKN09