The PS4 uses standard keyboards like you'd use with a PC, except that it can't recognize the sort of extra keys some gaming keyboards add. So a fancy Razer gaming keyboard that adds a bunch of extra programmable keys would be wasted on it. Go with a basic USB or wireless keyboard and it should work fine.

If you go with a USB keyboard, just make sure the cord is long enough. I use this one with both PS3 and PS4: http://www.amazon.com/gp/product/B000ODP9H2
It's just a standard USB keyboard like you'd use with a PC except that it comes with an 8 foot long cord to better suit typical TV to couch distances.