In this paper, we propose a persuasive ambient display to promote walking exercise. The display is originally a daily object like a mirror, and provides information about one's exercise level on the periphery of a line of sight. Four strategies for walking encouragement are specified as hypothetical motivational elements: 1) pleasurable interaction with information obtained through daily activity, 2) supporting reflection on each day's walking, 3) avoiding negative feeling while providing negative feedback and 4) facilitating inter-personal encouragement. A case study on information presentation is presented to see the feasibility and effectiveness and to explore further requirements, where a mirror is augmented.