Wheelchairs and prosthetics present a unique problem, because there's no practical way to screen the person separate from their hardware.

Canes are another matter entirely. Every checkpoint should have non-alarming canes and they should be pro-actively offered to any WTMD-eligible pax using a cane or walker who is otherwise forced to use the NoS or get a grope. The NoS isn't even always an option because some of these folks have balance issues and can't hold still long enough for a successful scan without their cane or walker (not to mention it's a potential safety hazard).