Theoretically it would shuffle around and be different sizes each time, so it would never be quite the same. And you could alternate shoes to mix things up a little more.

Of course if you're the only one with gravel maybe that would stand out. Which is why we need to get everyone on the same gravel-based onion network :P

We could make a shoe that shifts water around in the sole over time.

Kind of like active suspension in a car, it would randomize your gait but I suspect it won't be so easy and that a certain arms race of detection vs confounding / mimicking would ensue.