Here is a robot that can be controlled by a protester while he/she takes a break or spend time doing other things. ProBot is built using a Beaglebone, Matsushita GMX-6MP013A DC Motors, WiFi module, megaphone, Sabertooth 2X25 motor driver, and a few other parts.
This self-balancing robot has a sturdy frame with a megaphone on top as a simple of protest. This video shows it in action:
[Source]