Turntable speed apps

Not sure if this is the right place to post a suggestion. For those selling turntables, can I suggest, for the convenience of potential buyers, that sellers download a phone app like RPM (for iPhone), to verify that the turntable is spinning at the right speed, whether it be 33.3, 45 or 78. Just activate the app, place the phone on a spinning platter and check the readout. Very easy. I'm sure there is an equivalent app for Android as well. Thanks for reading. Apologies if this is the wrong space to post this.

While Thank you so much for a kind soul like razzwill...

I have tested the App and compared with Actual Strobe Disc on the platter rim.  Found some slight discrepancy in the speed given by the App.

Those who like to print their own Strobe Disc on A3 paper, send me a PM

or go to Vinylengine