Review on XOSS X1 Bike Speed and Cadence Sensor: Wireless Bluetooth 4.0 Computer for Accurate Bicycle Speedometer (2 Pack) by Dan Phillips

As long as you have a gap of 3 cm, it's fine! The device is very small and after a quick upgrade I put it on axis (speed monitor). For cadence it's like a regular bike, nothing special needs to be done. It's very easy to adjust your cadence or speed, just remove the battery and switch modes. The connection to the XOSS G+ monitor was fully automatic and immediate. But I don't like the monitor: it is VERY small and it is mandatory to install the app on the mobile phone with location and bluetooth enabled to change anything on the monitor. Not a big fan of this part.