Are there any GPS programs or plugins which would display GPS info on a 4 line by 20 char parallel LCD display?
Although the answer is no, not that I know of I think the question needs more detail. It wouldn't be hard to display heading, direction, altitude and lat/lon but I'd question how useful that really is. A couple o fus tried to do something like this using the Destinator SDK to indicate the next turn and how far away it is but they don't really make that info available.
So... basic GPS info... shouldn't be hard. Useful routing info... difficult. Someone here is writing a MapPoint extension to do better routing, in theory that could be enhanced with an LCD output I guess.