"My Other Suit is a Kiton"

Once all airports introduce full body scans, an opportunity presents itself to transmit surreptitious messages and pictures hidden in the structure and fabric of one's clothing. Words could be easily composed with thread patterns, and carefully arranged patches of denser material could readily create detailed images.

Of course the downside is that only the folk operating the scanners get to read them, unless the idea is linked to that of earlier one here, and printouts of the resulting scans are offered for sale to passengers for a small fee.