This info has been posted several times but the max physical extension of the tablet holder is 170 mm, which
just fits the iPad Air or iPad Air2. Obviously, the iPad mini 2 or 3 will fit. Some have asked if the iPad 4 (older than the iPad Air or Air2) will fit and the answer is no. It's 186 mm wide.
So get our your wallet and head down to the Apple store or wherever and get ready to spend some serious coin.
BTW, DJI recommends that any iOS device have at least the A7 processor for reduced latency in the video feed. The Air has A7, the Air 2 has A8x (Faaast!). WiFi only is fine, since RC has GPS built in, unless you want cellular for other purposes. Hope this helps.