Wireless communications and device miniaturization are enabling pervasive scenarios where the limited resource availability and the wide heterogeneity of access terminals make crucial to provide mechanisms and tools for the dynamic adaptation of Quality of Service (QoS). Particularly in case of very resource-consuming services QoS levels should be downscaled to fit the specific characteristics of the provisioning environment and of the current access device. In this context, a challenging aspect is to account clients not only for the generated network traffic, but also for the distributed resources involved in the dynamic QoS adaptation. The paper presents an accounting middleware solution that extends the traditional Internet where and when needed, depending on the mobility patterns of the wireless client devices, by introducing flexible mobile components for metering and charging. The middleware exploits the Mobile Agent (MA) technology to achieve dynamicity in metering/charging beha...