It looks like it's in the works and due in the 5.x release cycle. http://blogs.unity3d.com/2014/07/03/metal-a-new-graphics-api-for-ios-8/
I wonder how do you use it? Is it going to be applied automatically upon compile/testing for iOS devices? Or do you have to manually call various functions?
Like written in the blog post. Compute shaders will not be there in 5.0 just yet, but we are working on making them available. Current plan is to make same ComputeShader assets (DX11/XB1/PS4 only now) work on Metal, GL ES 3.1, GL 4.3+ etc. However that's quite some work and won't be finished in time for 5.0.
That sounds great! I was curious about how you would implement them, but as it seems they will be created the same as other computeshaders when you eventually implement them, I have nothing to worry about! I can just sit back and wait for 'someone' (you of course) to do the hard work