Use iPad as Preview Monitor with DSLR (nikon)...possible?

No...

Sorry, but no.

The closest thing I've seen to this is this app:

http://www.ononesoftware.com/products/dslr-camera-remote/

It supports only some models of camera, and requires the the camera be tethered to a laptop, to which you then connect wirelessly from the iPad. I don't know if that would be useful to you, but it might be worth a look.

And while not a preview app, ShutterSnitch might be useful in your workflow.

As wireless camera systems become more common and functional, we may eventually see remote-control apps that can connect directly to the camera, not requiring an intervening laptop. This is already partially possible for photographers with a Leaf or a Mamiya digital back.

Regards.

Somehow, my response to your question did not make it live, either my error or Apple censorship. Here it is again, if it does not last, Apple does not want you to find a solution to your question.

So, if you have an SD card capable camera, the answer to your question is YES, you can preview photographs wirelessly and instantly to your ipad.

Search youtube for... ipad wireless photo tethering

Russ

It looks unlikely that the iPad will ever be useful as an extra screen. I think you may have found the best option, which is to use a portable DVD player.

Other options include; look into buying a self powered monitor for your camera, or just using a small netbook style laptop as you can get stands for them to attach to a tripod, a final option is a tablet PC most of the new ones can run the nikon NX2 camera software.

Hope that helps.

Gordon