I am on a similar task but still in design phase. Can share experience in a couple of weeks.
Thanks. Looking forward to it. I will be doing some research as well.
This isn't going to be entirely inside of the application because Insert From Device is not supported outside of filemaker go. So you can't use the "capture" actions that are available in FMGo for WebDirect.
I haven't tested it on mobile recently, but more likely you're going to use the insert file script step, which will allow the user to choose from the camera roll (or whatever the android equivalent to that is) and select a photo that's uploaded.
I was thinking along the same lines. So far my research has led me to believe that that is the only viable approach at this time.