Which in turn e.g. a camera (only horizontal) in the direction of the person moves / rotates and actionable.
well i guess you want to move a camera in a single axis if it is so it is well within capabilities of arduino as richard said prepare a grid of sensors and check which one is triggered and move the camera in the +ve or -ve direction based on the postion of the sensor triggred it can be acheived using a servo - hopethis helps
Probably the simplest setup might be have an Ir heat detector panned by a servo scan for something warmer than ambient. When a hot object is detected have the cam servo pan the cam to the same servo position where the IR servo detected the heat.