A review is given of the exceptional electrochemical performance of epitaxial InN/InGaN quantum dots (QDs) as photoelectrode for solar hydrogen generation by water splitting, as biosensor transducer and as anion-selective electrode, also evaluated as supercapacitor electrode. The performance is benchmarked against the best performances of other reported materials and nanostructures. A model based on the unique interplay of surface and quantum properties is put forward to understand the boost of catalytic activity and anion selectivity, interlinking quantum nanostructure physics with electrochemistry and catalysis. Of equal impact is the direct growth on cheap Si substrates without any buffer layers, allowing novel device designs and the integration with Si technology. This makes the InN/InGaN QDs viable, opening up new application fields for III-nitride semiconductors.