There is an XMPP standard for link-local messaging. It's supported in Empathy through the telepathy-salut library. In other words, it's installed by default on

There is an XMPP standard for link-local messaging. It's supported in Empathy through the telepathy-salut library. In other words, it's installed by default on Ubuntu (though you need to turn it on) and presumably other distributions. It'd be nice to see mobile apps supporting this standard, too.