Over the past decades, the field of redox biology has witnessed a profound expansion in the catalog of known redox-active compounds, revealing their critical roles in cellular signaling and homeostasis. Paralleling this discovery, the toolbox of genetically encoded fluorescent indicators (GEFIs) has evolved to enable real-time, specific monitoring of these molecules within living cells. This review synthesizes key studies employing GEFIs to investigate redox dynamics in vertebrate models, covering a spectrum of physiological and pathophysiological contexts. A critical analysis of the architectural designs, operational mechanisms, and performance parameters—including advantages and inherent limitations—of prominent GEFIs is provided. Finally, we explore the constraints of traditional fluorescence imaging methodologies in complex in vivo settings and consider label-free methods for detecting redox events using Raman spectroscopy, FLIM.