the iphone doesn't have a live jtag, does it? you can only use the jtag interface on hardware if the hardware is cooperating (by design) with you, it isn't a magic wand you can wave and get everything... additionally, ios does on-flash encryption of the data partition and you need the phone online to read it (or to get the key), so even if you could get some magical jtag port to give you up all the blocks that store user data, it would be encrypted...