Speech is a unique and rich health signal: no other signal contains its singular combination of cognitive, neuromuscular and physiological information. However, its highly personal and complex nature also means that there are several significant challenges to overcome to build a reliable, useful and ethical tool suitable for widespread use in health research and clinical practice. With hundreds of participants and over 18 months of speech collection, the Remote Assessment of Disease and Relapse in Major Depressive Disorder (RADAR-MDD) study incorporates one of the largest longitudinal speech studies of its kind. It offers a unique opportunity in speech-health research, the investigation of throughout the entire data pipeline, from recording through to analysis, where gaps in our understanding remain. In this presentation, I will describe how our voice is a tacit communicator of our health, present initial speech analysis finding from RADAR-MDD and discussion future challenges in relation to the translation of speech analysis into clinic practise.