If you are going with a visual piece of tape, then you could replace the arduino with a simple mobile app that recognised the tape via camera and transmits speed via UDP to the app. I wonder if the camera on a typical phone could keep up ?
You could do the same with an inductive sensor wired to the headphone jack. This worked for Square to read magstripe data, which is significantly more complex of a signal to parse than simply counting the number of local maxima per second.
Inductive sensors are cheaper, simpler and more foolproof; cyclists have used them for decades to gather both wheel speed and cadence.
Slightly off topic:
You make an interesting point about Square.
In the context of Apple Pay, the move to take away the headphone jack suddenly makes a lot of sense (for Apple).
exelius|10 years ago
Inductive sensors are cheaper, simpler and more foolproof; cyclists have used them for decades to gather both wheel speed and cadence.
treebeard901|10 years ago