We present a system [1] that allows wireless smartphones to be used for mathematics communication, that is, for the creation and exchange of mathematical formulas, diagrams, and text between two or more participants. The system enables two or more persons with smartphones or traditional computers to participate in a session. Each of the participants may convey textual, graphical and mathematical information to the other participants. Users can draw, edit, and label geometric shapes, send chat messages, and compose formulas. A turn taking mechanism moderates the communication. The system also supports the integration of services that can be used to provide individual users with additional functionality. Currently, a LATEX rendering service is available to allow users to create and share mathematical formulas in typeset quality. Wireless smartphones are becoming the medium of choice for improvised synchronous collaboration since increasing numbers of users carry their smartphones at all times. It is true that the small size of the devices---while necessary for their ubiquity---limits the complexity of collaborative tasks that can be carried out effectively. On the other hand, there is a need to capture inspiration, to access and evaluate information on the go, and to make decisions on the spot. The domain of mathematics is ideally suited to explore---and push---the limits of smartphone communication. The challenge of representing mathematics in typeset form has led to the development of document preparation systems such as TEX, LATEX, and LYX which are in widespread use today. Mathematical handwriting recognition continues to push the limits of general handwriting recognition [2]. Many of the cognitive challenges that arise in mathematical collaboration also arise in intellectual teamwork in other domains. Some of the challenges of developing a system for mobile mathematics communication are posed by the input and output limitations of the devices and the enormous heterogeneity of the available hardware platforms. We use the Treo 600/650 as our hardware platform. Our software is written in pure Java and can be run on any platform that supports the Java Virtual Machine. Our software architecture makes it easy to add new local or remote services to enhance the communication. The poster presents use-case diagrams, architecture diagrams, and a series of screenshots that describe the user's interaction with the system. The poster also shows how we solved the problems of cross-referencing and turn-taking in mobile collaboration. A 7.5-minute video shows users interacting with the system.