The next update of Music Box Composer will bring MIDI file export to both mobile and the desktop versions of MBC - in addition to auto advance when entering via the Piano strip, improved PDF export, and the optional 30 note key mapping for mobile (desktop versions have this option already). Should be released in a few days for Desktop, ...
Version 2.1, with a new Piano Mode for both feedback while creating and modifying notes, as well as note editing by piano key, is now available on both iOS and Android.
Slice of bread is (finally!) available on Android. Google Play Link
Download from iTunes.