This mount can be used to add a speed sensor to an exercise spin bike, with the appropriate size hub on the flywheel.

Specifically, I have a Pooboo 525 bike, and Moofit speed sensor. Speed sensors seem to be similar sizes, however the bike flywheel hub is more likely to vary. This is one of the generic Amazon brands, so Sunny and others may be similar.

No speed sensor mounted on a regular exercise bike will give fully accurate speed readings, but this will at least allow apps to recognize movement.

I used supports for the slight overhang.