Are you drying hardwoods or softwoods? Hardwoods are typically controlled by ~24" long board samples that are weighed daily, manually. There are load cell systems available that can be used to weigh these samples continuously, with the weight being recorded by the controlling computer. Generally it is still a good idea for the operator to go into the kiln daily for inspection of the lumber.
Southern pine is often high temperature dried in under 24 hours and samples are not taken. There has been the use of load cells that weigh the carload of lumber to track drying used in lab kilns. One limitation is that we generally do not know the starting moisture content closely enough to pinpoint accurately the ending MC.