At the end, the author suggests getting an iPod Touch. A friend I just visited in NYC does this. My friend has an iPod Touch he uses to make Google Voice calls when wifi is available (which is most of the time). He also has a dumbphone for making calls/texts when they're absolutely necessary and wifi isn't available. The dumbphone is prepaid with a very small allowance of minutes and costs him $10/mo.

I felt inspired by this setup, but the truth is I do rely on using Google Maps when in unfamiliar places, and that requires a data connection. To a lesser extent, finding local business listings/reviews without wifi comes in handy, too. I don't need it all the time, but when I do, these features are crucial.

If it were possible to refine my friend's idea by using only one device (say an unlocked Nexus 4), and getting a small prepaid data plan as well (say 500MB/mo), I'd consider doing the same. Does that exist?