Martingales with barrier reflections are a fantastic way to model all kinds of parameters that are randomly distributed over time, but stay roughly the same value in the short haul. They're also very well studied, so you can make strong guarantees about their expected values and distributions, unlike naive random walks that stay within a given range.

We published a paper about such an application to modelling sensor error here: https://doi.org/10.1177/1932296817711297

The martingale comes up under the "simulator" section, starting in the paragraph "In our previous simulation study".