In most current biomedical monitoring applications, data acquired by sensors attached to a patient are either transmitted directly to a monitoring console for real-time processing, or they are simply recorded on the sensor unit for deferred analysis. In contrast collecting and transmitting biomedical data continuously over long distances in outdoor conditions is still a challenge. In this paper we investigate the possibility of using disruption-tolerant wireless sensors to monitor the cardiac activity of runners during a marathon race, using off-the-shelf sensing devices and a limited number of base stations deployed along the marathon route. Preliminary experiments conducted with a few volunteers running around a university campus confirm that this approach is viable, and suggest that it should scale up to a real marathon.