The use of handheld computers in educational contexts has increased considerably in recent years and their value as a teaching tool has been confirmed by many positive experiences, particular within collaborative learning systems (Mobile Computer Supported Collaborative Learning [MCSCL]). The cost of the devices has hindered widespread use in schools, however, and cell phones have emerged as an attractive alternative. To test their functionality as a platform for collaborative educational activities, the authors adapted an existing Personal Digital Assistant (PDA) application for use on cell phones equipped with Wi-Fi. This article examines the problems of developing applications for this alternative technology and reports on a usability analysis of a collaborative classroom activity for teaching physics. The results confirm the viability of the cell phone platform, taking due account of the device's processing, network and interface limitations. With an appropriate design, users quickly master the technology, though a certain decline in efficiency relative to PDAs is observed. (Contains 6 tables and 3 figures.)