CAN interface
You can get a can tranceiver from microchip, and also a lot of pic's support can. It's a two wire, half duplex, differential signal, normally down a twisted pair. It is a protocol that is built on layers, like tcp/ip. At the transport level, it sends packets of data of up to 8 bytes, with an identifier, packet length, and data. These are broadcast, all nodes receive them. The nodes use the identifier to decide what to do with the message. The identifier is like the address. It also has sophisticated error detection, correction and collision avoidance. This is all done in hardware. (Thank f--k)! The protocols that are built on this can get very complex. Such as reprogramming and updating software in situe, troubleshooting and tweeking engine maagement, heads up displays, you name it! It is used extensively in the motor industry. All cars talk can!