The SuperKEKB electron-positron collider at the KEK laboratory in Japan aims to achieve a maximum luminosity 50$\times$ higher than its predecessors KEKB and PEPII, positioning the Belle II experiment at the forefront of searches for non-standard-model physics in the next decade. High collision intensity implies high beam-induced radiation, which can damage essential Belle II sub-detectors and SuperKEKB components. Twenty-eight diamond sensors, read-out by purpose-built electronics, are installed in the interaction region to measure radiation and prevent damage. This talk introduces the system features and discusses its performance in early Belle II data taking.