R Twitterer ech0chrome reports that (s)he has successfully installed R on an iPhone. I haven't tried it myself, since it requires jailbreaking the iPhone, but full instructions have been posted to the R Wiki. It seems that once you have Debian installed on the iPhone, it's simply a matter of installing the required Debian packages. Seems like a neat hack, but I'm not sure how productive I'd be typing R code on that small keyboard, even with the complete 5-row keyboard available on jailbroken iPhones. Now, if you could run R on the iPad (early reports of it being hacked are coming in already), that might be another story.