At the limits of physical representation of bits, novel opportunities arise, in particular leveraging the granular nature of charges, photons and atoms. One interesting application is the generation of truly random numbers. The need of a true random sequence of numbers is strategic for a variety of applications, ranging from the game industry to cryptography. Physical sources that rely on natural phenomena spanning radioactive decay, chaotic oscillators, thermal and quantum noise have their own merit, but for the purposes of integration, attributes such as bandwidth and power consumption, need to be accounted for. Here we evaluate transition metal oxide two terminal devices, memristors operating near the quantum of conductance and negative differential resistance metal-insulator transition devices, as potential candidates for a solid state source. In particular, the caveats of each implementation will be covered, such as the necessity of postprocessing and scalability.