Audiobus: Use your music apps together.
What is Audiobus? — Audiobus is an award-winning music app for iPhone and iPad which lets you use your other music apps together. Chain effects on your favourite synth, run the output of apps or Audio Units into an app like GarageBand or Loopy, or select a different audio interface output for each app. Route MIDI between apps — drive a synth from a MIDI sequencer, or add an arpeggiator to your MIDI keyboard — or sync with your external MIDI gear. And control your entire setup from a MIDI controller.
Download on the App StoreAudiobus is the app that makes the rest of your setup better.
Comments
I used to own an old school Ensoniq sampler. You had to do looping by ear. You had to nudge the edit points little by little by pressing a button to nudge things forward or backward by course and then fine amounts. Isn't that a lot like what @Spookyzoo says is currently built in? If so, all is not lost!
@Crabman: We are so used to see the waveform when editing, but people have been cutting tape with precision many many years before that
Use your ears!
Good point ;-) And i have to admit that"totally useless"was a bit harsh,that's definitely not the case.
DP
I've been using Audioshare to cut and trim all the waveforms in my Nave preset bank. Most are only a few milliseconds in the end, so thank god for those "nudge" controls.
Another thing people might miss that's not obvious at first is that when you choose "trim" and drag those circles, the further down you drag your finger while holding the circle, the finer the movement will be. Makes it all really really easier and faster to edit when using that. I wouldn't mind a slightly tweaked edit window with a bit more zoom-able details for those few pesky ones you just can't get right though, but using the ears also works wonders 
I can't see the screen if I use my ears to drag the circles...
I just tested the trim function for myself, and I am very satisfied with how it works! Its similar to my old Ensoniq EPS sampler! Works great! :-)
Now we just need an option to apply a modest crossfade to de click loops, and we're set! :-)
@ Audiojunkie, I thought you might have been using the Ensoniq Mirage like me but the EPS was quite a step up from 12 bit sampling to 13 bit sampling :-) .
Just wanted to express here how AudioShare has become quite the de facto for me in audio/MIDI management.
Keep up the great great work, @j_liljedahl .
@Keebo It was a dead easy-to-use sampler, but mine was overheating for some reason. My 3 1/2" floppy drive was intermittently failing to load, and floppies were becoming increasingly unreliable. It weighed a ton! Funny thing is, SampleWiz has so much more power and is so much easier to use than my EPS ever was, and most people don't think of it as a real sampler. Heck, I'm no better, because I'm always complaining about there not being a good standalone multisampler for the iOS platform. :-) We really do have it good! Especially considering the masterpieces that have been created on 4-tracks! Hehehe! :-)
Yep, I should have added too that the trim function has 2 side bars that can swipe the in and out points anywhere on the waveform. (For anybody who doesn't have Audioshare and was interested.)
@PaulB: use a mirror like the rest of us!
I tried a mirror, but all my audio clips came out backwards...
In ref to the clicks; I use to have the same issue, here's what I do now. When working on a loop or sample I use my finger to drag as precise as possible, play it and hear a click, jump down to the fine tune move buttons < & > and try it one notch, listen, try another, listen. With this method i find that I can get rid of almost every click within 5-7 notches either left or right. If left doesn't seem to get better zero it and start trying right (if that fails switch ends of the sample and do it). It doesnt take long. I leave it playing while doing it because if the click comes from the beginning you can tell if its gone immediately because the loop resets each time you move a notch. Very rarely do I have to edit both ends if the sample to get rid of it but patience will get rid of it and then you don't have to degrade with fade in/out.
Sorry this is so long I'm tired and overly talkative (typetive?)
good stuff.
@JMSexton While it is true that there are many zero point crossings that come naturally in a typical audio file, there are many times when the natural zero point crossings do not coincide with the location in time or the proper blend of the sound to make the sample appropriate. In short, there will be many times when "where" you want to cut will click if a crossfade or at least a steep fade in/out is not applied. I'm not referring to standard 4/4 130bpm drum loops, but rather looped audio of many sustained instruments--such as an ARP Solina, for example. Much of the high quality instrumental looping that is found in many of the high quality sound libraries today borders on the realm of the dark arts (kidding) but also a lot of skilled good luck. While no one is likely to use Audioshare for any work like what I mentioned, it is in the realm of probability that someone will come across something frequently that clicks no matter what you do, if you need to slice the audio at a certain particular spot and loop it. This is where a simple option to add a crossfade can be a lifesaver. :-)