wear a hat/beanie with IR LEDs, you need a few frequencies of "IR", but it's invisible (or barely visible) to humans, but it's the same as shining a light into a sensor to a "machine". could have it built in to a jacket collar, too. you'd have to wear pants to foil gait detection, too. Something with a lot of angles and squiggles that is hard to see as "distinct" against the background.