There are similar uncertainties between many measured quantities, though the product of the uncertainty is not necessarily hbar/2. For example, the three scalar (orthogonal) components of angular momentum have a similar relationship in which the product of the uncertainty in any two of them must be greater than hbar/2 times the average magnitude of the third component. Gravitational potential and mass density, electric charge and electric potential, range/distance and Doppler/velocity (as in radar measurements), time and frequency, etc.have similar uncertainty relationships. In general, any two measurable quantities related to one another through Fourier transform duals (one is the Fourier transform or inverse Fourier transform of the other) have an inherent limit in the precision with which they can be simultaneously known. These are traditionally called Heisenberg uncertainties only when they are physical measurements. Other fields have similar terms (radar ambiguity function in the case of Doppler/velocity and range). Importantly, the limit is not the precision with which they can be measured, but it is fundamental in that they cannot be known more precisely than this uncertainty. A simple sine wave and its frequency helps enlighten the concept for me. As a sine wave (say a light wave) propagates, its frequency becomes increasingly well defined, but the time/space required for the measurement becomes increasingly longer. There is a limit to how accurately the frequency can be known in a given amount of time/space.