I'd actually recommend Wal-Mart Family Mobile over Straight Talk. The reason I didn't chime in previously was because he was talking about being a poor student, but his phone of choice is the newest iPhone. Once you start talking Wal-Mart FM, Straight Talk, whatever ... you are buying your own phone. Is he ready to commit $700+ to this?
As a Clark Howard listener, I've heard complaints about Straight Talk, but forget if it's more than their customer no-service.
Regardless, Wal-Mart FM has unlimited plans, just like Straight talk, and others. Unlimited talk, text, data.
With Wal-Mart FM you get a couple options:
$29.88/month - with 1GB of 4G LTE data
$39.99/month - with 3GB of 4G LTE data
It's unlimited because after the cap, it throttles to a lower speed. I think I use about a Gig a month. And I'm often lazy about turning on my Wi-Fi (a lot of the time it's off). But I also don't use music streaming services (which I'd guess is the one app that will use tons of data - since you are most likely to use it while driving and away from Wi-Fi).
I could get away with a Gig.
But the other issue is where he lives. As someone that doesn't live in the boonies, my reception is great. It works when I'm driving (minus some tiny dead spots here and there), works in my office (and I also have WiFi there), works at home (and I also have WiFi There), works pretty much everywhere when I'm driving around my town, or hitting up stores/friends/bars/places in my state.
But if I lived in say certain areas of Maine or New Hampshire or something ... it could get sketchy and your only choice might be Verizon.