The best I've ever had
These days almost everyone has a smartphone of one make or another. And I myself dont go on a ride without my phone (obvious safety issues), so why not combine your phone with some small and very lite cycling technology? The case is nice and sturdy, it locks well so if it falls it doesnt look like you will have to go out and buy a new one. The speed/cad sensor is small and easy to install. Plus its all wireless, woo-hoo.
Good as any
My first speed/cadence (S/C) sensor stopped working after a few months, but Wahoo support replaced it for me free (So I LOVE their support!) All makers of these sort of sensors (e.g., Garmin) require very close proximity of the magnets to the sensors so installation is key. I installed my S/C sensor upside down and it works just fine - perfectly, really. The reason I do this is because the spokes are moving in a direction that would be very damaging to both sensor and wheel if the sensor moved too close to the spoke. By mounting it upside-down, I am in no danger of the sensor tearing up my wheel. Like I say, it works just as well for me this way. I wish someone could make a unit that did not have to have the magnet sooooooo close to the sensor, but nobody does. I highly recommend Wahoo sensors!