Ставь крон на каждые 10 мин.

$timearray=array('1:50','3:40','5:30','7:20','9:10','11:00','12:50','14:40','16:30','18:20','20:10','22:00');
foreach($timearray as $time){If($time==date('H:i')){echo'ONline';}else{echo'OFFline';}