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Dipole–Dipole interactions (DDI) constitute an effective mechanism by which two physical entities can interact with each other. DDI processes can occur in a resonance framework if the energies of the two dipoles are very close. In this case, an energy transfer can occur without the need to emit a photon, taking the name of Förster Resonance Energy Transfer (FRET). Given their large dependence on the distance and orientation between the two dipoles, as well as on the electromagnetic properties of the surrounding environment, DDIs are exceptional for sensing applications. There are two main ways to carry out FRET-based sensing: (i) enhancing or (ii) inhibiting it. Interaction with resonant environments such as plasmonic, optical cavities, and/or metamaterials promotes the former while acting on the distance between the FRET molecules favors the latter. In this review, we browse both the two ways, pointing the spotlight to the intrinsic interdisciplinarity these two sensing routes imply. We showcase FRET-based sensing mechanisms in a variety of contexts, from pH sensors to molecular structure measurements on a nano-metrical scale, with a particular accent on the central and still mostly overlooked role played between a nano-photonically structured environment and photoluminescent molecules. [ABSTRACT FROM AUTHOR]