Recently, mobile computing devices have led to the wide distribution of wireless network. Handheld mobile devices combining wireless multimedia and diverse App with value-added service have created the convenience and personal using experience. This has made App become a driving engine of communication service and changed the cognition of people towards mobile computing and smart life. Location-based service (LBS) enables services to provide smarter user experience, not only orientation recognition, but also positioning services such as PUSH service in aggregated area. Therefore, applications related to positioning are increasing recently. To solve the problem of unable to answer calls for users, this study utilizes Android to develop an Auto SMS reply App which can switch the mobile to vibration or silent mode. When users have fixed schedule or unavailable to answer calls, they can edit message to reply and send this preset message to callers when they can't answer the call, making communication between people easier and diverse.