The interlocking-based strain-gauge sensor presented here can detect multiple ‘skin-like’ mechanical loadings (pressure, shear and torsion) using metal-coated, high-AR polyurethane-based ...

But at some point you may actually need to measure torque, in which case this guide to torque sensors might be just ... but in the end a $20 bag of strain gauges and an LM358 were the quickest ...