In Bot-free IRC notifications, chiselwright describes the beginnings of a IRC notification app for iPhone.
I've done something similar in the past, with irssi scripts that forward highlights to my email account and send an SMS when it sees a summons. I've been running it for over a year, now and it has been a great tool for keeping up on questions directed at me on IRC without having to be online all the time.
My code was based on other irssi notification scripts, so in the spirit of contributing back to chiselwright and anyone else interested in such apps, my code is freely available in my git repository.
See you on IRC.