Lets review.
I tried to see if you could hook up a PC to a digital picture frame. No go
Digital picture frames use USB or SD card and they are media capable. You could most likely rig a Picture frame to play from a PC, but still not what your looking for.
A Wifi Would require drivers which a digital picture frame does not have, it is essentially just a play back medium (a monitor). A wifi would also require its own voltages. You would also have to be able to configure it.
I would think your best bet would be using say an iPad. It has what you need and can be stood up like a picture frame. One caveat, the price. Rediculously high for what you need.
So to answer your question. In the price range of even a High end Digital Picture frame, there is no such device that will do what you want it to do.
Work around: Video Camera to baby's room over PC. Then VNC to your iphone or G1/Nexus.