The 80 knot take-off roll check of the captains and copilots ASI's in the 737 is really a gross error check. Not five knots or even 10 knots, because even as the call-out is made, the aircraft is accelerating so quickly that the speed comparison is useless a second or so later.
From simulator experience, by the time either crew member focuses on the standby ASI for comparison purposes, another 10-20 knots has passed by. Boeing do mention use of the ground speed reading as a confirming factor since rarely does one see a defective ground speed read-out. Of course any ground speed check must take into account the wind component.
What is important though, is what happens if the PNF does not call out "80 knots" either because he had his attention elsewhere, or he simply was too slow to react or of course if his ASI had not yet reached 80 knots.
In that case, it is encumbant on the PF to make his own call-out based upon his own ASI - for example "going through 95 knots my side." In turn, this should stir the other pilot either to agree or not agree or remain bemused. The latter is more likely given the time factor.
All the time the aircraft is accelerating towards V1. Believe me we see this in the simulator a lot when a fault is set into one or other of the main ASI's. There is immediate doubts in both pilots minds.
This is where a knowledge of expected ground speed is good airmanship and rather than risk a high speed rejected take off under the circumstances, the next best thing is to rotate on the expected ground speed reading allowing for the wind component.
Provided the pilot applies commonsense knowledge of initial climb pitch attitude coupled with known N1 for the circumstances, the confusion of which ASI is the problem can be sorted out later at relative leisure. Sorry about thread drift