TouchDAW is a full-featured DAW controller combined with some general purpose MIDI tools running on Android™ devices and recent Chromebooks. It allows you to remote-control most DAW software and may also come in handy as a side-controller for keyboards or in situations where you might just need some MIDI source, but happen to not have your keyboard or controller around.
The app was started in 2011 - on a tiny HTC Wildfire running Android 2.1 - out of curiosity for the new computing platform and to make those early smartphones usable as control devices for some artwork. The underlying network MIDI library originates in work done for a large machine-theatre project and the sensor to MIDI functionality originally drove a virtual guitar feedback installation. Never had I imagined that the project would last as long as it did, but despite my curiosity being more than satisfied, I still find myself investing far more time into it than what I should allow myself to.
TouchDAW works with RTP or multicast MIDI over WiFi. It is directly compatible with Apple's MIDI Network implementation in Mac OS X, Tobias Erichsen's rtpMIDI for Windows as well as ipMIDI on all major desktop OSs. Various types of Usb connectivity are available as well, and you can - with some caveats - also run MIDI over Bluetooth.
Quickstart Video (YouTube) Manual
Please use the free version to 'try before buy' and test the waters before making that substantial 4 Euro investment.
APKs contain both tablet and phone layouts. As it is pretty much impossible to cram all the functionality of the emulated hardware into a proper phone UI, most recent phones will let you optionally use the tablet layout.