DAISy Hat – AIs Receiver for the Raspberry Pi
shop.wegmatt.com
shop.wegmatt.com
Also, awesome board, if I sailed that'd be a good (and small) backup. Slap gps, a solar cell, batteries, screen, storage for maps, maybe even throw in a wideband transceiver for comms and have an all-in-one backup nav console in box.
It is also the cheapest option for an IP feed with AIS data I know of.