This paper aims to discuss the roles for the two types of tracking user behavior. Considering these two types of tracking, sensor based recognition has a great advantage when sensing human activity, but it is not always adequate when tracking in the real world. In this paper, we compare the benefits and drawbacks of sensor-based tracking versus self-reported data in persuasive applications called EcoIsland. Keywords Self-reporting, Automatic Sensing, Persuasive Technology ACM Classification Keywords H.5.2. User Interfaces: User-Centered Design