May be used to measure the stress (deformation of material) with the optical technique named photo-elasticity. So you have a mechanical piece and contemporaneously a sensor.
The key to using SMPs in applications is determining the material response and developing a model which can accurately predict the material behavior. The ability of SMPs to recover large strains combined with its low weight and low cost advantages has produced much interest in design applications. For instance they can be used in biodegradable sutures, repairable automobile skins, satellites and other space vehicles and morphing wings etc.