All you need if you plan to use Sprint's roaming services is either the Sprint 3G/4G USB Modem 250U device or Sprint 3G/4G U600 USB Modem, as well as Sprint SmartView EVDO connection manager.
According to Sprint's 4G president Matt Carter:
“With these agreements, Sprint is kicking down the door to 4G international roaming and taking a first step toward allowing people to enjoy 4G service wherever they are around the globe. We’ve taken the 4G leadership position in the U.S. and are now proud to partner with visionaries Digicel and Global Mobile to solidify our international leadership role.”
We hope that Sprint wouldn't overcharge for its international 4G roaming services and this is really the first step towards expansion of the third-largest carrier's roaming capabilities worldwide.
source: Sprint via BGR