There are many accidents that occur in home every year, many of which are fatal and often involve with young children under the age of 4. Although many innovative applications using WSNs (wireless sensor networks) technology have been developed, little attention has been given for protecting children from potential harms and risks in the home environment. This paper reports our work on the design and implement of an Adaptable Infant Monitoring System (AIMS) using TelosB sensor motes. AIMS system is an open-source tracking and monitoring system with minimal cost, knowledge and time to set up. For performance comparison, three different localization algorithms are proposed and implemented in the system. Extensive tests under different scenarios demonstrated the working of the prototype system.