Well, to be clear, I meant the Coospo sensor with magnets. It's the older one that they sell, and technically I would assume it's almost identical to every sensor of this type. The internals are probably made OEM by some factory somewhere, with a different outer casing. I use this with various phone apps through BT without problems, except that the speed sensor is a little too far from the magnet on my spoke, so I stuck a piece of rubber underneath it to push it closer to the magnet. The wahoo sensor and various other brands look
identical similar except that those other speed sensors are encased in a rotating arm that can be adjusted closer to the magnet, but the length of the arms is too short to reach my 20" wheels, so the Coospo sensor worked for me with the sensor attached to an extended cable.
If you're talking about switching cadence and speed by removing the battery, then you're referring to the magnetless sensor. I don't have any experience with that magnetless sensor, but generally they work by using an accelerometer, like the one in your smartphone. It needs to interpret the changes in
magnetic fields acceleration to detect each revolution. I read that sensors of these types sometimes give false values on bumpy surfaces. Accuracy would probably depend on how the software in the sensor decides which readings to throw away. I also don't want them activating during transport, since it's possible that you'd have to take out the battery to get them to stop activating (although I'm not sure about this point). A sensor with magnet is more consistent since it's a much simpler tried-and-true mechanism of a magnet passing over a switch.
