HS Rockets already synchronize in samp. I remember once that a guy fired hs rocket on my rustler and his rocket followed me for about 400-500 meters and then took my rustler down.
I guess this depends on the servers. In some servers heat-seeking rockets actually follow the planes, well all the vehicles (car-bike-plane-boat). But in some gamemodes this option is preferably disabled.
I had also seen that the hs rockets sometimes follow, sometimes not. If the hs rockets never follow the targets in the server you play in, you should ask about it to the high level admin.