Aging is a burden for society mainly due to insufficient care for elderly. New technologies offer a complementary solution. We analyze ethical issues of these technologies. Several experiences are shown. One using electrical signals detected from electro domestic appliances used by the old person living alone. Other using actigraphy in the hospital using passive infra red sensors. This work is based on nocturnal activity a reference parameter to evaluate differences in activity in presence of cognitive problems, depression or different levels of autonomy. Results show the importance of depressive symptoms on nocturnal activity in controls and the paradox effect on patients with dementia. Nocturnal activity can be useful in the follow up of therapeutically effects, as shown with a patient registered during 79 nights. Actigraphy was used as gold standard to validate a semi qualitative scale about nocturnal behavior. These experiences show the reality of the concept of environmental actigraphy.