Cydia Impactor is a GUI tool for working with mobile devices. It has features already, but is still very much a work-in-progress. It is developed by saurik (Twitter and website).
You can use this tool to install IPA files on iOS and APK files on Android. It also can help you exploit the series of Android “Master Key” vulnerabilities.
Note: Do not “Run as Administrator” Impactor; doing this makes drag/drop of files not work on Windows 10.
For iOS, if you are using either Windows or macOS, you definitely need to have iTunes installed for this tool to work (for different reasons). You do not need Xcode installed to use Impactor (even for features such as signing IPA files).
To download new versions, use “Check for Updates…” under the Impactor menu from inside of the application. Impactor will also occasionally prompt about new versions that come out.