An apparatus comprises: a memory to store sensor data and at least one processing core that compiles a message based on the sensor data； the message is transmitted from the apparatus to a server, causing receiving in the apparatus from the server of a machine readable instruction that comprises reference data of a predetermined activity type； estimated activity type is derived by comparing the sensor data to the reference data. The sensor data is preferably acceleration sensor data； additional sensor data may include sound or vibration data. A server, methods and a computer program are also disclosed.
