What are some alternatives?
When comparing Stetho and GapDebug, you can also consider the following products
Chrome Mobile DevTools - Mobile Debugging Tools
Bugsee - See video, network & logs leading up to bugs or crashes
Xcode - Xcode 4 is the new version of Apple’s powerful integrated development environment for creating great apps for Mac, iPhone, and iPad. Xcode 4 includes the Xcode IDE, instruments, iOS Simulator, and the latest Mac OS X and iOS SDKs.
Genymotion - This is an Android emulator for your computer.
Instabug - The top apps in the world rely on Instabug for beta testing, user engagement and crash reporting.
Flipboard FLEX - At Flipboard, we place a high value on tools that speed up and improve the development process.