Mobile phones have evolved into complex systems as they have more and more new applications built-in. As a result, they are less reliable and less secure than before. Virtual Machine Monitors (VMM) or hypervisors have been intro- duced to help the reliability and security of mobile phones but the existing research does not completely address three issues critical to mobile phones: real-time support, resource limitation, and power e±ciency. In this paper we propose building a new VMM called MobiVMM for mobile phones to deal with these issues. MobiVMM enables real-time support using priority based scheduling and a pseudo-polling mech- anism. Resource and power e±ciency is achieved through light-weight design and implementation, highly customized guest operating systems, and a virtual hardware abstraction layer. We present our design considerations and report some preliminary experimental results based on the OMAP 2430 development platform.