A 17 ohp blood spot machine would be good.  i.e. if the levels were above a certain level---you would  need not give the shot.  That could go by blood tests done first thing in the morning.  They should experiment a little and determine what the GH levels are at certain times and what this reflects in the 17 OHP levels at the same time.  That way they could devise a reference range that determined what the GH levels were likely to be at that time.  They  would need to make a machine similar to a blood glucose machine that gives an immediate read out.   YOu could then determine from that if GH shot was necessary the following evening.   I cannot see that happening due to the fact that there would be so little demand for them--or they would be very expensive to acquire.