I have an Ixus 100IS (or SD780) which has one of the dual function USB/Video outputs. There are various sites out there that point out if you get your hands on a connector like this one
http://www.sparkfun.com/products/9167 (also known as ExtUSB and used by HTC) you can use the USB pins to trigger capture, and the video pins can still be used as output.
However, I want to be able to use PTP to trigger the camera using the computer and download the image straight away. Therefore I would need all four USB pins and a USB connection operational (as opposed to just the two signal pins required for USB remote cables). Has anyone tested this as working, so that you can have the live video and the USB connection running at the same time?
While the device also has HDMI, it's only active during display mode (so anyone has ideas on getting that working during record mode, they're also welcome)