Sensor based context management

According to an example aspect of the present invention, there is provided an apparatus comprising a memory configured to store first-type sensor data, at least one processing core configured to compile a message based at least partly on the first-type sensor data, to cause the message to be transmitted from the apparatus, to cause receiving in the apparatus of a machine readable instruction, and to derive an estimated activity type, using the machine readable instruction, based at least partly on sensor data