Today RootMetrics brings its free Cell Phone Coverage Map app to Android. Like Speedtest.net, the RootMetrics mobile app tests your phone's signal strength and upload and download speeds at any given time. It also goes a step further to compile the voice and data strength of other RootMetrics users across carriers into a single coverage map of major urban centers in the U.S.
CNET Senior Editor Kent German and I used the iPhone version of the RootMetrics app to pit the Verizon and AT&T iPhone 4 against one another in a data speed showdown around San Francisco. You may have also seen the RootMetrics carrier coverage map on CNET's own Web site. (RootMetrics is a CNET partner.)
The crowdsourcing feature of the RootMetrics coverage map is secondary to testing your personal data speeds and signal strength, but it's still informative for ballparking the state of cell phone coverage in America. In addition to collecting data from real-life users who run speed tests on their phones, RootMetrics also adds some of its own data to the apps (RootMetric's business model includes selling granular data reports to carriers). The company uses an "aging algorithm" to weed out older data from the maps, which goes a long way toward keeping data fresh.
In general, it's always a good idea to take diagnostic testing from an app with a grain of salt. The results don't always align with your own personal experience, because of variable factors like your precise location and the time of day.
The RootMetrics Cell Phone Coverage Map works on Android 2.2 Froyo and Android 2.3 Gingerbread smartphones, and is available in the Android Market.