A html5 web app for mobile safari to upload images from the Photos.app?
UPDATE:iOs 6 Safari is going to support upload videos and images from the Photo Library.
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I hate this word, but, it's impossible (up now). Here is the reasons:
1) mobile safari doesn't support upload anything.
2) mobile safari can't access ios components (actually it can, but, only through phonegap)
another way to approach this problem would be to give users a private email address that they can email their photos to for automatic upload (eg. photos+abc123@yoursite.com).
A little more work to set up, but will give a consistent experience for users on all devices (and non-mobile users might find it convenient too).