theres a short thread in the gear section, I went with the Scala and it honestly works great with the phone/ 1 other rider. Adding a third and its kind of strange since you cant three way talk on it at all.
i have a sponsorship with them for motocross... they sent me a bluetooth equiped element helmet, not a Shoei but very good sound and function for bluetooth.. can go between riders as well.. its plug and play fully installed in helmet if you want to get a pair of helmets for chatting with a backseater, could be a less expensive option.