A method for monitoring Internet of things, loT, device state, the method comprising: in a service capability exposure function, SCEF, implemented using at least one processor: providing a common interface for receiving subscription requests from loT application servers, ASs, or service capability servers, SCSs, for monitoring state of loT devices of plural different generation networks; maintaining, in the SCEF, a database of identifiers of loT devices of a network of a given generation; providing, in the SCEF, an interface to a subscriber data repository node of said network of a given generation; receiving, via the common interface, a subscription request for subscribing to receive state information regarding an loT device; performing a lookup in the database and identifying the subscription request as being associated with an loT device registered in said network of a given generation; and in response to identifying the subscription request as being associated with an loT device registered in said network of a given generation, transmitting, via the interface to said network of a given generation, a message to the subscriber data repository node for receiving state information regarding the loT device, wherein the common interface comprises a T8 interface, said network of a given generation comprises a 2G or 3G network, the T8 interface is further configured to receive subscription requests for state information regarding a 4G or 5G loT device, and wherein the method further comprises, transmitting, via an interface to a further network of a different generation to said network of a given generation, a message to a node in the further network for subscribing to receive state information regarding the 4G or 5G loT device. providing a common interface for receiving subscription requests from loT application servers, ASs, or service capability servers, SCSs, for monitoring state of loT devices of plural different generation networks; maintaining, in the SCEF, a database of identifiers of loT devices of a network of a given generation; providing, in the SCEF, an interface to a subscriber data repository node of said network of a given generation; receiving, via the common interface, a subscription request for subscribing to receive state information regarding an loT device; performing a lookup in the database and identifying the subscription request as being associated with an loT device registered in said network of a given generation; and in response to identifying the subscription request as being associated with an loT device registered in said network of a given generation, transmitting, via the interface to said network of a given generation, a message to the subscriber data repository node for receiving state information regarding the loT device, wherein the common interface comprises a T8 interface, said network of a given generation comprises a 2G or 3G network, the T8 interface is further configured to receive subscription requests for state information regarding a 4G or 5G loT device, and wherein the method further comprises, transmitting, via an interface to a further network of a different generation to said network of a given generation, a message to a node in the further network for subscribing to receive state information regarding the 4G or 5G loT device.