The app takes about 210Mb as it contains IDE, compiler and uploader. Make sure you have enough free space in internal storage and it can't be installed on sd card because of Android security policy.
* open/edit arduino sketches
* example sketches and libraries included
* customizable code syntax highlighting *
* compile sketches (no root required)
* upload sketches (Arduino Uno/Uno_r3, Duemilanove, Nano, Mega 2560, Leonardo, Micro/Pro Micro, Pro, Pro Mini boards are supported, android devices with USB-host support required)
* works offline (no internet connection required)
* code complete *
* real-time diagnostics (errors and warnings) and fixes *
* file navigator *
* tiny built-in software keyboard *
Advanced paid features (marked with *) review:
(c) "Arduino" is a trademark of Arduino team.
ArduinoDroid - Arduino IDE Screenshots