Sensors capable of detecting different types of biomolecules have widespread applications in the field of biomedical research, but despite many years of research, the development of biosensors suitable for point-of-care (POC) applications in resource-limited areas is still extremely challenging. Sensors based on photonic crystal hydrogels (PCHs) hold much promise in this regard because of their numerous advantages over other existing bioanalytical methods. All current PCH biosensors are however restricted in the types of analytes they can detect sensitively with good selectivity. By taking advantage of the powerful and ubiquitous antibody-antigen interaction, we report herein the first-ever competition-based PCH biosensors capable of naked-eye detection of various biomolecules (e.g., proteins, peptides, and small molecules) with high sensitivity and selectivity and minimal background and excellent reversibility. We showed such PCH designs could be extended to the fabrication of different enzyme-detecting biosensors. The universal feature of these novel biosensors thus enables future development of POC biosensors in disease diagnostics for other bioanalytes.