Because the movement at the sensor has to be tiny (something like a few millimeters), I'm thinking of mounting the otolith on the long end of a lever. That's great, but it means the force will be magnified by the same proportion and the sensor has almost no resistance either. So the lever will also have to supported by something else to take the lion's share of the weight. Shock absorber?
And speaking of absorbing shocks, what about bumps? The contact forces will all go down (or up) at the same time, perhaps unevenly. I may have to specify smooth terrain. But how does a human do it? Is that why we have fluid in our ears, to keep things from rattling around in there?
(Of course, I'll probably have to specify smooth terrain anyway, since a wheel, especially at Lego scale, isn't very good for bumps.)