The iPhone (4) is expensive enough as it is. It doesn't make sense to me to spend even more to make it do what it doesn't do out of the (very expensive) box. Especially since editing anything on an iPhone (or other smartphone) is like cleaning your house with a toothbrush: technically it is possible, but nobody in his right mind would like to do it IRL!
Like my carpentry teacher taught me in the very first lesson 45 years ago: use appropriate tools for the task at hand! Don't hammer in a nail with a screwdriver!
A dinky phone is not an appropriate tool for editing HD movies...
