This returns true if you're on a single node erlang application :P

    erlang:node() == nonode@nohost andalso erlang:nodes(known) == [nonode@nohost]

A single node erlang application would be one that doesn't use dist at all. Although, if it includes anything gen_event or similar, and it happens to be dist connected, unless it specifically checks, it will happily reply to remote Erlang processes.