The right to data protection is a highly developed area of law in Europe. At the same time cloud technology has become a routine part of the European citizens' digital life. One relevant development is medical sensor networks, which are seeing increased use for monitoring health and well-being for e.g. of elderly people living at home. The large amount of data generated by such sensors indicates that it would be suitable to employ a cloud-based solution for processing and storage, but since the sensor data represent sensitive personal data, there are many challenges that must be addressed. This paper identifies and explores a number of accountability obligations that arise.