Some adjustment is required once every piece is mounted. Both magnetic sensors must stay in close range of 3-5mm with the main unit. There is an LED on the main unit that indicates the connectivity status, it blinks green whenever the sensor is detected or passes through it. The technician at LBS should know how to install if you are not comfortable with DIY.
Some advised not to use such sensor if often go off road. It makes sense that the sensor might not be built for such environment i.e. muddy, wet etc. I do not know the "ruggedness" of this sensor, Motorola did not provide any info at all.
p/s: You can check out my other MotoActv related posts here.