Precision dairy farming can be defined as the use of sensor technologies to measure the physiology, behavior and production of individual animals for the purposes of managing the herd or individuals within the herd. With increasing herd size and automation, the regular intimate contact between the farmer and his animals is decreasing, and in some cases being replaced by technologies that could serve the function of identifying individuals or groups of animals which need attention because they are diseased or in distress. In the context of dairy cattle health and welfare there are many sensors and systems that have been developed to monitor or detect mastitis, metabolic disease, lameness, calf disease and overall cow comfort. This review will highlight some of the currently available technologies, including their associated opportunities and challenges. The opportunities to use inputs from multiple sensors to inform robust decision support systems are intriguing. However, there are 3 major issues that limit the widespread reliance on these sensor technologies at this time. First, most sensor systems have not been thoroughly evaluated and validated against appropriate reference methods or across a broad range of animal and farm environments. Second, the decision support systems underlying these technologies are often simplistic, not transparent to the user, and don’t make use of the broad range of inputs that are often available. Third, there is a lack of experience, expertise and support among dairy herd advisors who are working with dairy producers trying to incorporate these technologies into their management programs. Until these issues are addressed, the widespread reliance on precision dairy technologies for managing dairy cattle health and welfare will not reach its potential.