Remember the wobbly white sphere sentry that kept Patrick McGoohan a prisoner in the cult series of the same name? Well, here is a slightly more robust and capable modern version.
The Rotundus Groundbot can nip along at an impressive rate and would seem ideal for patroling large flat areas.
Maybe they could roam the strees of our towns and cities after dark as an additional security measure.
The could be mounted with paintguns loaded with indelible dye ammunition to further help identify miscreants.
Find out more about these globular automatons here.