The FP6 project "Wireless Accessible Sensor Populations" (WASP) has developed an end-to-end infrastructure for the deployment and enterprise integration of wireless sensor nodes. The infrastructure is generic and allows for optimisation for a variety of applications by the development of dedicated services that can be distributed over (wearable and ambient) sensor nodes, the WSN gateway, and the enterprise (backend) system. Key to many applications, such as elderly care considered in this paper, is to optimise the battery lifetime of wearable sensor nodes that can be (remotely) customized to the monitoring needs of individual persons and to the quality-of service demands for offered services. The WASP infrastructure provides practical solutions for these targets and is being validated for realistic elderly care scenarios. These scenario's aim to support the elderly in (semi-) independent Ambient Assisted Living settings as well as to provide health workers with effective means of studying transient deterioration and behavior changes characteristic to the ageing population.