I’m documenting this publicly just in case anyone ever runs across the same problem I’ve been having.
I occasionally plot out routes on Google Maps and save them under My Maps. Curiously, there is no convenient way to get My Maps onto my iPhone. This leads to the slightly ridiculous situation where I would need to print out maps to bring with me.
Google Earth for the iPhone purportedly will access My Maps, but I couldn’t get that to work, because I sign into Google through Google Apps for Your Domain; there’s a web-based sign-in inside Google Earth, and when I attempted to sign in through the GAfYD (launched through the Google Search app, which otherwise works great), it would throw an error.
I have discovered if I log into Google Earth through the non-GAfYD interface, using my full e-mail address and the usual password, it works.
From what I understand, there’s only a limited ability to show personal maps in in the Maps app on the iPhone, and this can only be done via some hackery. Google Earth seems like the best option for accessing personal maps.