confirm my flights have gotten in okay as I travel, checking in with Google Latitude;
meet my friend Tessa, by exchanging text messages when I arrived at Aeroparque;
confirm a charitable donation I'd made two days ago did make it in for this tax year, by calling the charity's 1-888 number;
clear a travel hold on my credit card account, by calling their collect number.
In the before-mobile (B.M.) days I could do all these things, of course, but just with more difficulty. I could find an internet cafe to send e-mail, I could make contingent plans to meet people, and I could place calls from my hotel room. But those all take time, away from the point of traveling, and they don't always work (dialing internationally from hotel phones is expensive and occasionally not possible). And it's not just any mobile phone -- I pity anyone on Verizon or Sprint because those phones won't work in Europe, Asia, or South America. So, hurray for this modern marvel and indispensable travel accessory.