  Overtourism occurs when the number of tourists exceeds the carrying capacity
of a destination, leading to negative impacts on the environment, culture, and
quality of life for residents. By monitoring overtourism, destination managers
can identify areas of concern and implement measures to mitigate the negative
impacts of tourism while promoting smarter tourism practices. This can help
ensure that tourism benefits both visitors and residents while preserving the
natural and cultural resources that make these destinations so appealing.
  This chapter describes a low-cost approach to monitoring overtourism based on
mobile devices' wireless activity. A flexible architecture was designed for a
smart tourism toolkit to be used by Small and Medium-sized Enterprises (SMEs)
in crowding management solutions, to build better tourism services, improve
efficiency and sustainability, and reduce the overwhelming feeling of pressure
in critical hotspots.
  The crowding sensors count the number of surrounding mobile devices, by
detecting trace elements of wireless technologies, mitigating the effect of MAC
address randomization. They run detection programs for several technologies,
and fingerprinting analysis results are only stored locally in an anonymized
database, without infringing privacy rights. After that edge computing, sensors
communicate the crowding information to a cloud server, by using a variety of
uplink techniques to mitigate local connectivity limitations, something that
has been often disregarded in alternative approaches.
  Field validation of sensors has been performed on Iscte's campus. Preliminary
results show that these sensors can be deployed in multiple scenarios and
provide a diversity of spatio-temporal crowding data that can scaffold tourism
overcrowding management strategies.
