Necessary ?, can't see them developing it if it wasn't tbh.
I like them as they are DESIGNED by themselves, EMERALD, or rahter KARL at EMERALD did this, used to be built in house but so busy now farm this out.
They fit straight on certain cars with no mods needed, rovers, lotus etc and can use any sensor configuration.
They have a one off mapping price of £250, regardless of how long it takes, and can be security coded as on rover cars.
tabetha