Arduino/Android Powered Autonomous Drone

I'm looking to develop an autonomous drone using an Arduino interfaced with an Android phone. The Arduino and phone will be mounted inside of an RC plane. All I'm looking for the Arduino to do is control the motors/servos of the RC plane based on input from the Android phone. My question is, how difficult is it to interface an Android app with an Arduino board? Are there any tutorials on doing so, or does anyone have any advice?

Thanks!

their are multiple ways to interface with arduino.
Wifi Shield
direct USB with arduino IOIO and phone
Bluetooth
audio jack
http://www.amarino-toolkit.net/
Android->arduino with RC transmitter -> plane

if it is in the plane, IOIO or the audio jack interface would probably be the best for direct connect. the IOIO is a special Arduino board that costs more, so you could use the audio jack method with a regular Arduino. The amarino toolkit simplifies things a lot but uses Bluetooth(could be slow/unreliable). IOIO would be next easiest maybe. depends on your programming/electronic experience. amarino maybe, and IOIO for sure, use JAVA

Awesome! Thanks for the information and links!