The average temperature measured by all the thermometers is used to generate a cicada sound the higher the temperature, the louder the cicada . An instrument draws attention to itself when there is a change in the value it is monitoring.
A user requiring information about a site (textual meta-data) can place the notepad at a site. A page with the text then appears above it. A user requiring a photograph taken at a site (graphical meta-data) can place the camera at a site.