Most accurate IOS app for turntable speed check

The KAB strobe with battery powered strobe light is old fashioned but the best I know about. The battery power assures that the strobe light is spot-on accurate.

skos, I have used it. The flashing lights may be as accurate as you describe, but following the location of the light beam on a wall as the LP rotates is fraught with the probability for human error which in my mind makes it very difficult to get a measure of rpm commensurate with the potential of the instrument. For me, it is a gimmick.

Sutherland Time Line. It is accurate to about 2 parts per million.

There is no way that anyones eye measuring a moving spot on the wall is accurate to 2 parts per trillion, so whilst it sounds impressive, it does not in of itself provide an accuracy check anywhere near what is claimed.

Personally I have found the KAB to be very good. ( Best value ) It is also easy to check the speed with the stylus playing on the record as well ( outer part of record ).

Shknspin2 is really good if you want to see how your TT is performing with wow flutter etc.

RPM and other apps I have tried are not accurate. Results are inconsistent. They are only good for entertainment - not calibration.

Record based speed checking systems are garbage - they only work if there is 0 eccentricity in the vinyl record, and the hole is the exact same size as your spindle ( but those 2 conditions are seldom the case.

SOTA's  RoadRunner is not only a tachometer but it continuously monitors and makes micro adjustments in real time to achieve 33.333 or 45.000 rpm.  

This table sounds amazing,  it is pitch perfect.