Tethering to smartphone works
The new Sony Experia Z has native USB host support, which means you can tether your camera directly to the phone - no dongles required. All you need is a micro-USB plug at both ends of the cable (use an adpter if you can´t find a micro/micro cable). The phone has a 5" FHD screen.
I have D/L Helicon Remote for Android, hooked my D800 up, and it works nicely. You can set most things from the app, e.g. to store RAW on camera and JPG on the phone (or just a copy).
One obvious feature of Helicon is shooting focus stacks. It works, even if not as quickly as if you tether directly to a computer - of course. But "in the field" it will be ok.
Naturally tethering to a tablet will give you a better view, but the point here is that the phone suits your pocket while the tablet doesn´t....and you will most likely carry the phone anyway.
You can also have the Experia Z wirelessly hooked up to a computer while you do your shooting, but I haven´t had time to check whether you automagically can view the pictures as they are being shot - you can however access the phones gallery.
I just got the Experia yesterday evening so I haven´t had time to work everything out