I wonder if crowds in a chaotic situation (e.g. a riot) can
be made more smarter, if everyone had a visual/sound
signalling system.
E.g. A RGB colour glow wand or disk with set of predefined
buttons, that is clothing mountable.
With the right set of rules, you could provide tactical
information
about a kettling in progress etc... (e.g. Lots of
people pressing red lights, thus showing a sea of red along
the line of conflict)
It could also be tied to a radio system, that could vibrate
based on the number of colours it receives from nearby
participants.
pros: No smartphones needed. Real time visual feedback to
everyone else.
cons: No privacy of communication. You hold the wand,
you get arrested.