Cameras, in Spearbreakers usually taking the form of Camera "Spikes," are an electronic security measure employed widly by various companies such as Ballpoint or Eris and used by Mr Frog , who uses some crude magma-steam system he has hidden to power his own electronics, though what he uses for remote cameras is not touched on and presumed to be batteries he has smuggled in.
There are of course a few different kinds.
The most commonly seen in Spearbreakers are remote cameras mounted on stakes driven into the ground. They are small enough to go unnoticed and it takes a keen eye to see them. Besides patrols, F.R.O.G.s and Terrahex's scouting missions into the countryside, these are the fortress' main early warning system.
Normal cameras placed in dark glass nodes to prevent people from seeing where they look. They're not too spectacular, and more obvious ones are just simple security cameras ona pivoting mount.
Some security cameras are acually point-defense sentry guns and not to be trifled with. While most tend to be propellant driven machineguns, Parasol is known to use small railguns and Eris prefers laser turrets.