[Aqua_Geek]

The sensor typically goes on the back of your upper arm (your tricep). You can accidentally bump into things with it, but it was infrequent enough that it didn’t bother me.

The needle is only used in the application of the sensor. It’s spring-loaded and retracts after the sensor is attached. I hate needles, but I found that the tape on the sensor provided enough stimuli to overwhelm my brain and not really feel the needle when it went in.