The unprecedented rise of mobile, internet-enabled devices across the globe has created a new field of "digital epidemiology". From small-scale studies of high-resolution contact networks to large-scale digital disease detection systems, we are witnessing a revolution in data availability and access that is continuing to affect every single aspect of human health. I will present some of my ongoing projects involving wireless sensors, social media data, and image data that reflect both the opportunities and the technical, social and organizational challenges around this rapidly evolving field.