We have just added CAN bus sniffing APIs to the Arduino library for Freematics ONE+. A simple CAN bus sniffing example sketch is also added.
CAN sniffing is interesting if you are have some insider information or good at reverse engineering, so some vehicle data outside the scope of standard OBD-II PIDs can be extracted.
Another product supporting CAN sniffing at the moment is Freematics OBD-II UART Adaper V2.1. This post has some information about the AT commands for CAN sniffing.