Weechat, the terminal based client, also supports a protocol like this. There aren't really any nice graphical clients for it, but there is a mobile one which is very usable, and there's an HTML5-y one, but I haven't tried that.

If you like irssi, but wish you had a better way to use it on mobile, you might like Weechat - that's how I use it currently, terminal over SSH on desktops, mobile client over the relay protocol on the go.