Digital photo frame, upload pictures while slideshow running?

I'd like to use a digital photo frame as a secondary display. I know I can use dual view with two monitors, but I want a small second display showing a few pictures. I'd like to be able to write a simple program which creates a picture with some readings from sensors and then copies it to the frame which displays it. The program is not a problem, it's the hardware I'm having problem finding.

I've tried a couple of frames in the $150 range and they all seem to have the same limitiation. There is no way to have the frame connected to the computer with usb and at the same time show slideshow. When connected they go into a 'image copy mode' and a slideshow can't be shown. I tried one with wifi but it could only fetch pictures from picasa and flickr, and update from those places were not automatic while showing pictures.

Anyone used a photo frame which can handle to show the pictures in the memory card and allow me to copy files at the same time and have them included in the slideshow? I guess I need to go up a bit in price?

Anyone with other ideas than this?