The term "mobile lessons" is coined for lessons held outside of "artificial" environments, such as classrooms. During these lessons, all actors are mobile and must move to do the required tasks. Themes tackled in such lessons may be as varied as geography, history, ecology, and linguistics. The use of mobile lessons is not a new teaching strategy, but new mobile devices may render it more efficient and more attractive. The aim is to place students in conditions germane to the ones in which experts work. The authors implemented in Java a software for creating and using mobile lessons and for monitoring students on the field. Contents and questions are in XML. Using this software, teachers of a high school in Sardinia (Italy) developed and experimented with a mobile lesson on the archaeological site of Nora. Under the light of this experiment, a wireless, distributed and more sophisticated version of the software is under development. (Contains 13 references.) (Author)