Damien Depends on what you expect out of them. If you want them for limiting belt fighting, a sufficiently advanced belt should be enough. If however you want them for posture or attire enforcement...
Electromagnetic thigh bands certainly would be an advantage by allowing pantyhose or tights over the belt even if the bands sit very low. A sci-fi anchoring system could even allow them to sit lower without being slipped over the knees. An intelligent distance control feature would be able to limit stride length and sitting posture more gently than a rigid chain, allowing for healthier, more dynamic sitting, safer walking and easier use of stairs and ladders. Toilet visits with underwear over the belt would be simplified by being able to slide down underpants beyond the bands.