The box I used to pull this off for a demo was a PC with a TV card. Any old desktop PC might do. Just add a TV card for the capture step.
I have this monitor - http://accessories.us.dell.com/sna/productdetail.aspx?c=us&l=en&s=gen&sku=320-0657
And I know form reading the instruction manual that it supports the following resolutions:
720 x 400, 640 x 480, 800 x 600, 1024 x 768, 1152 x 864, 1280 x 1024
I also have a PS3 Slim and want to connect to this monitor. There is no official cable for this but there are many ways of doing it.
I decided to purchase this box - http://xcm.cc/xcm_1080p_vga_box.htm
However, I didn't realise that this box doesn't change the resolution, it just changes the video and audio.
Unfortunately, in the UK where we have PAL the minimum resolution on the PS3 is 576i or 576p. As you can see my monitor does not support that or any of the other resolutions available. - http://manuals.playstation.net/document/en/ps3/current/settings/videooutput.html
I was wondering whether there was some sort of box or cable that I could connect to my monitor that would change the resolution before it was shown on the screen.