The Wahoo RPM speed and cadence sensors are easy-to-install bike sensors that provide data by both Bluetooth Smart and ANT+ connectivity.
They are small and don't use magnets, which is a massive improvement over the bike sensors that you have to fiddle around with to line up. They are easy to install, too: you take the sensor and insert it into its rubber housing then strap it around your wheel hub (in the case of the speed sensor) or cable tie it around your crank arm (in the case of the cadence sensor).
The battery lasts for ages. I've been using them for over six months now, and they still have plenty of battery left in them.
The speed sensor is a bit of a pain to install, though. You have to stretch out the rubber and spend ages trying to get your hands inside the spokes to hook it around the catches that keep it secure. Luckily, it only takes a few minutes, and you only need to take it off when you need to replace the battery.
The data seems mostly reliable, but I have seen some occasional spikes where an unrealistic speed is reported. I found the data slow on Zwift: anywhere from 3-10 seconds behind the power, I was putting down. Outside, it consistently responds within a few seconds on my Garmin head unit, so I think a large part of the problem is Zwift rather than the sensor.
In this video, I'll show you both of the sensors, and I'll also show you a close-up of me installing the speed sensor on my back wheel.