If the carrier for your smartphone is Sprint, you can check voice and data coverage using the Power Network Coverage Tool, an interactive online map. Just visit the page, type in your zip code (or the zip code of your travel destination) to find out if Sprint or Nextel offer adequate coverage.

Strength of voice and non-3G coverage is indicated in shades of green, while orange shades indicate cellular-broadband (3G) data coverage.

You can also check to find out the locations of towers built recently (within the last 90 days) and the locations of towers that are planned to go operational within 120 days.