I use Opsite (for those leisurely soaks in the tub). works like a charm. http://www.smith-nephew.com/professional/products/advanced-wound-management/opsite/opsite-flexigrid/
HOWEVER, it sticks to the sensor so well, that removing the Opsite tape will likely pull the sensor off.
The answer is to cut a circle of paper and place it between the sensor and the tape, so that the tape goo only attaches to your arm and the paper, not the sensor.