Sensorly shows realistic cell service coverage maps
Sensorly is a handy service where users can volunteer to share information about the 4G/LTE signal strength they get on their iPhone or Android-based smartphone, and that data is then aggregated to show exactly where the strong or weak signal areas are. The darker the color on the map, the stronger the signal is.
Sensorly is available as an iPhone app, too
The Sensorly website lets you enter a city and carrier to see coverage maps, as well as maps showing upload and download speeds. The iPhone app does the same and also includes a built-in speed test tool. You can choose whether or not to share your speed test results, and the app maintains a history so you can see if performance changes over time.
Sensorly is free to use both through the website and iPhone app. The Sensorly app is a free download at Apple's iTunes-based App Store.