Developer Steffen Nyeland has a blog post up where he shows how to build a dual camera app using Delphi XE6 Firemonkey. I think I’ve tried this before myself and came to the same conclusion that he did. Basically you can’t use both cameras at the same time on most devices which means you have to take one photo and then take the other photo (verses taking them both at the same time). He sets up some life cycle events to take care of disabling the camera when the app is in the background. He also sets up the camera buffer events to save the images off the camera buffer to a bitmap. He has code for merging the two images from the front and back camera. And finally there is code for sharing the final image using the share sheet action.There is full source code for his sample app available on the blog as well. I believe this code should work on Android and IOS. Additionally it will probably work in XE5, XE6, and AppMethod.
FMXExpress.com has over 700 tips and tricks for building cross platform apps on Android, IOS, OSX, Windows, and Linux with a single codebase and single UI using the FireMonkey framework found in Delphi and C++Builder.
FMXExpress covers top cross platform secrets for FireMonkey in C++Builder and Delphi XE5, XE6, XE7, XE8, Seattle, Berlin, Tokyo, Rio, and Sydney.