IMHO, for IVAO, you can try to parse IVAO whazzup data, and compare it to your pilot's flight data. If something match (can be vid, and/or callsign, and/or strings at the remark), then the system tag it online per whazzup download. So you have to set minimum value for the whole flight to be reported as online flight.
Or you can try for their private APIv2, which require token for an approved VA.
But, still i can't write a code for that, so i would like to know too..