Nickel-titanium-based alloys (NiTi) are the most important representatives of the shape memory alloy class. By characterizing the transport properties such as resistivity, Hall and Seebeck coefficients combined with spectroscopic data, we investigate the role of electrons in the martensitic transition leading to the shape memory effect. Strong changes in the charge carrier density obtained by Hall experiments are an indicator for a strong electronic contribution to this phase transition. Interestingly, this change in carrier density starts long before the actual transformation and is also reflected in spectroscopic data of the same samples. Changes in composition, for example by alloying Cu, modify the transformation pathway, but not the actual finding of a very strong change in carrier density directly correlated with the phase transition. Together with this reduction in charge carrier density, the charge carrier mobility increases during the phase transformation. What does this mean? Such behavior is known from martesitic phase transitions, which have a metal-insulator character. Here, neither additional scattering events nor an altered electron-phonon coupling are usually dominant in the interpretation of the resistivity anomaly. Rather, the experimental data indicate a partial transfer of electron density from the free electron gas (austenite) to the bond (martensite). We interpret this in terms of the formation of a charge density wave phase, which would be consistent with the strong charge carrier reduction to this phase transformation and can also be supported by many literature references. This means that the shape memory alloy NiTi-X has a very strong relationship to many 2D materials and materials with correlated electron systems - much better known in the physics community than in applied engineering. Nevertheless, rules for electron-informed alloy design may be derived from this similarity.