New generations of telescopes offer the chance to discover and exploit new radio pulsars, either found in extreme binary systems or orbiting stellar and super-massive black holes. I will briefly summarise the current state of art and will present new results from searching and timing with the MeerKAT telescope as an SKA precursor. These include new discoveries as well as observations of relativistic binaries as probes of gravity, demonstrating the power of radio astronomy in providing unique and complementary insight into fundamental physics.