A couple of suppositions about this equipment.
1) An elemental headhunter point has 5 sensors to place (one per suit/dispenser). Each can be placed in a separate, otherwise eligible locations.
2) A unit with an active probe can use the sensor to spot for another unit, at a net modifier of (+1 for indirect +3 for sensor) +4 to the shot before the spotter's movement and separate attack modifiers. (A unit with an active probe and LRMs would suffer the same +4 penalty for indirectly firing its own missiles.)
Are these correct?