Hot Wiring Polar Speed Sensor
I have not tried this as I didn’t need to run the sensor from the rear wheel, but it looks easy enough.
[url=http://www.roadcyclinguk.com/news/article/mps/UAN/739/v/2/sp/324962684566564502436]Polar Speed Sensor Upgrade[/url]
It will reduce battery life of the speed sensor, but that is user replaceable so no real issue.
Si.