Battery-powered mobile devices featuring wireless connectivity are becoming part of everyday life. In a functional breakdown of their power budget, communication accounts for a steadily increasing share of the total power; this is pushing research on power management of the wireless interfaces. The key to effective power management is power modeling. In this paper we describe a power modeling methodology featuring variable granularity and low computational burden, which can be applied to any wireless protocol. We apply it to Bluetooth and model two different BT modules, highlighting how different power management policies suit different implementations.