It is like it says, its a G-Force Sensor, helps to measure the HP at the wheels, gives damn accurate power figures (my mates Silvia was only 0.19HP off from the dyno...) and also gives accurate 0-100,0-400 ect times and it also compensates for wheelspins (doesnt do it without the G-Sensor)
Its not neccessary but unless you dont want your RSM to give your 'ballpark' figures, I would recommend you get it haha
Ya mate definately gettin it might as well use it to its full potential
Irlrs200 did u get my pm about the rolling road day as im not down as confirmed on the post