My idea would be to use a quad copter with FPV (First Person View) to transmit the camera image (camera on all the time) to a ground station, 7" RC monitor on a tripod, and control the camera shutter and zoom from the ground station transmitter via a USB connection to the camera. As it turns out the A2300 has an 11-pin USB connector which allows me to breakout the video separately and transmit video from the quad to the ground station.
For FPV with CHDK you have two options, neither especially good
1) Cameras can do TV out while in record mode. Many current cameras do not support this. Those with HDMI out consistently do not. Cameras with a separate composite TV out plug probably will do it. Cameras that put video out on the USB plug may or may not be able to do it, but if they do, you will need to make a splitter to have both video out and USB control. (see
http://chdk.setepontos.com/index.php?topic=5691.msg62525#msg62525)
edit: clarification regarding HDMI. It appears that some cameras like the s100 and s110 which support both HDMI and the USB output still allow you to use the USB output for shooting, while only allowing HDMI for playback.
2) Use PTP live view (through the USB port). This requires that you have a USB host computer on board the drone that is capable of running the CHDK specific PTP client. The computer must then have some way of doing video out. To use the existing live view client, you need a full desktop GUI, although with some coding you could do something more stripped down. A small SBC like a raspberry pi can be used, but it is unlikely the drones flight computer will be able to do it, at least not without significant programming on your end. PTP live view will also not give you great frame rates, resolution, or latency.
An alternative would be to do your FPV with a separate micro camera, although that would obviously give you less feedback about the actual zoom.
4. Would need to have an 11-pin USB port, I think, in order to breakout the video from the camera.
As noted above, this may not guarantee the camera will actually produce video out in record mode.
FWIW, I recently got an elph130 for <$100. I did the port and it is pretty complete. According to Canon specs it weigh 133 grams (CIPA standard, which presumably includes battery). Battery life isn't great, but probably a lot longer than a drone flight time. I can't tell for sure if video out in record mode works, but if I have the video out cable connected, pressing the shutter extends the lens and the screen stays black.
edit:
According to canon specs, the a2300 and a2500 are 125 grams (with battery). With 16 mp images, you probably don't need the additional zoom of the elph.
