Mobility modeling and analysis is a key issue in wireless networks. In this paper we propose a new and quite general random waypoint (RWP) mobility model which is valid over the entire plane. We derive key properties of the proposed mobility model including transition length, transition time and spatial node distribution. Then the RWP mobility model is applied to study the handover rate in cellular networks under both deterministic (hexagonal) and random (Poisson) base station (BS) models. Closed form expressions for handover rate can be obtained. These results show the expected property that the handover rate is proportional to the square root of base station density. Also, we find that Poisson-Voronoi model for BS coverage areas is about as accurate in terms of mobility (particularly handover) evaluation as the ubiquitous hexagonal model.