Fluorescent protein-based biosensors are providing us with an unprecedented, quantitative view of the dynamic nature of the cellular networks that lie at the heart of plant biology. Such bioreporters can visualize the spatial and temporal kinetics of cellular regulators such as Ca2+ and H+, plant hormones and even allow membrane transport activities to be monitored in real time in living plant cells. The fast pace of their development is making these tools increasingly sensitive and easy to use and the rapidly expanding biosensor toolkit offers great potential for new insights into a wide range of plant regulatory processes. We suggest a checklist of controls that should help avoid some of the more cryptic issues with using these bioreporter technologies.