I don't know but I have the first generation iPhone and it has trouble displaying each of the updates on the SPOT tracking pages. I imagine it would work similarly with the IRC site but the newest 3GS or whatever its called might actually work much better. Just call them at IRC and they probably by now have addressed the iPhone ability and I think they should develop a new IRC app for iPhone. Only thing is down in Mexico, coverage is sketchey and may not support 3G or 4G format.
i have used mine on ionearth i have a 3g not the new 3gs worked great didnt have the restriction of the antenna on the truck i also know that ionearth has there own apps they use to run the systems at the races