Required iPhone Knowledge for International Travel

PDA Mode

You can disable the cellphone antenna on the iPhone by putting it in airplane mode. By default, airplane mode also disables the wifi antenna. You can re-enable the wifi antenna independently of the cellphone antenna by clicking Wi-Fi and flipping the switch to on. This will allow you to access the internet without incurring roaming charges.

Textual Intercourse

One thing you'll miss is text messaging. Do not fret Littlefoot; in the days between snail mail and text messages, people sent emails. iPhone works great with emails. Set up your gmail account on your iPhone and check it whenever you get internet access.

If you need more immediate response times, get a multi-protocol iPhone IM client. There are several great IM clients for the iPhone that you can get for free. My favorites are Fring and Palringo. I like the Palringo interface a lot for IMing, but I like Fring for IM and Skype support.

Phone Home

Calling home is a lot of fun when you're on an international adventure so you can make all of your friends and family jealous. I'm a big fan of the Skype unlimited U.S. land line calling plan for $2.95 so that's what I use. Also, Skype-to-Skype calls are free. There may be better VoIP services out there, but I haven't found one yet.

So, how do you Skype on the iPhone? Like I said before, Fring supports Skype and multiple IM clients and has a decent interface. As a note, when you use Fring to make a Skype call, you have to put +1 before the area code and phone number (i.e., +17705551212). Skype recently came out with its own iPhone application but it's spotty at best for me; you may have better luck.

Social Networking

Facebook has a great free iPhone application to keep you in touch with your friends and family back home. If you tweet, I really like TwitterFon. TwitterFon conveniently supports twitpic too.

Finances

When you're traveling internationally, it's nice to be able to check on your bank accounts back home; however, it'd be pretty tough to get to every page you're interested in within the 1 hour of internet access you get for 5 billion euro. If you use Mint.com (and you should), then you can get the free Mint.com iPhone application and check every balance at once and get a detailed transaction list.

Literature

Search the iTunes App Store for literature you may want. You can find travel guides, maps, and translators. Also, search the internet for images relevant to your trip. For example, find a large image of the subway system and break it into sections so you can view it on your iPhone.