Unity3D struggling with iOS ImagePicker plugin Objective C

I've been looking for it over the Internet but I can't find something that really help me for this. I'm new about Objective C (started 2 days ago) and I've to develop an Unity3D plugin that enable me to pick an image stored in the Iphone from Unity. I heard UIImagePicker was the only way to do it, I've tried to use it but I'm struggling because it doesn't work like I want. I just need to open the image picker and get the path of the image selected, then I could use UnitySendMessage to send the path to my C# code. I wouldn't mind looking at a good sample code !

Thanks in advance.