Local magnetic probes have applications in several fields. In fundamental condensed matter physics, some of the most interesting outstanding problems relate to the behavior of strongly correlated electrons and quantum decoherence in electronic systems: electrons create magnetic fields, so ultrasensitive magnetic probes provide an important complement to more traditional measurements. Local magnetic probes also have applications in applied fields, ranging from the fairly mature but still fast-moving field of information storage technology to the emerging areas of nanomagnetic devices and spintronics. In this talk, I will survey the most promising noninvasive local magnetic probes for precision measurements. I will conclude with several examples of the applications of these probes to the physics of magnetic flux quanta in superconductors, including the ability to manipulate single vortices and the search for evidence of spin-charge separation in unconventional superconductors.