EDIT: Do not update to Xcode 7 if you intend to publish to the App Store until this issue has been fixed. Make sure background application updating is switched off on your Mac.
You need a Mac, XCode 7 (which up until a week or so ago was only available as a beta to people with paid developer accounts), and a free developer account.
I just put one of my Codea projects onto my iPhone and it worked great.
I had to turn off “enable bitcode” as described here: http://codea.io/talk/discussion/6874/solved-problems-with-xcode#latest
Give it a go, it’s a great feeling.
@yojimbo2000 one more information:
If you are using something like openUrl, Xcode will warn that http is not security. So, you need to do this:
Info tab → Add the key App Transport Security Settings, type Dictionary → key Allow Arbitrary Loads, type Boolean, value YES
Thanks for the tip @erickyamato
I’ve noticed that in iOS9, the first time you use openURL for app switching, it gives you a warning dialog. It seems to remember your response though, because each subsequent openURL executes without the warning.
You can’t submit to the App Store (of course) with a free account, but also it seems you cannot perform the pre-submission validation checks with a free account. So it’s possible that your app could run fine on the iPhone, but still not meet submission requirements (I think).
@yojimbo2000, you cn’t submit because you need have a certified (.p12) and another stuffs.
you are quite right @yojimbo2000! 
@yojimbo2000 do you have any idea if you can publish it to your own iOS 8 device or does it have to be an iOS 9 device?
That’s a very good question. Both of my devices are iOS 9 now so I can’t check I’m afraid.
ok, thx anyways, I hope someone else figures this out soon tho, would be nice to know
Do not update to Xcode 7 if you intend to publish to the App Store until this issue has been fixed. Make sure background application updating is switched off on your Mac.