Useful smartphone apps for musicians
 

Hi guys
I recently got my first smartphone after years of using the "dumb phones" and i want to fully exploit the possibilities of this device.
Can you recommend me any good apps for musicians?
I want to find especialy something good in these categories (i know its easy to search myself on google store, but there is like tons of apps in these categories so i want you to recommend me a specific one you find best)
1) metronome - I prefer some more complex metronomes that can play unusual time signatures since i am a realy big fan of 7/4,5/4,11/4 and polyrythms :D, it should also have not very annoying sound
2) guitar tuner - i only play acoustic guitar at campfires, so i need only basic tuning but it should be reliable
3) apps for ear training - intervals, chords, progressions, rythm, eq, eventualy singing
i need something to kill long times on train :D
4) anything that you find useful

Oh and it should be free or not very expensive, since i am broke college student :D