Correct, you will need to buy the BT module and mic, you can get them in a set for a decent price. Works really well and very clear. You don't even know it's there.
As for the Iphone, yes you can connect it using the item in the link you provided. I don't bother as once you have the BT module, you can stream music from your phone via BT. I also loaded up almost all my music onto the HDD, so no need for the MDI.
Not sure of prices nowadays, but I paid around £600 for my F about 5 or 6 months ago.