This is going to sound like a strange request but I use a couple of apps that allows you to take photos and then they use the photos in different ways.  What I'd like to do is instead of taking an actual photo I'd like to select an image that I've already got loaded on my phone and return that image to the app rather than a new photo.

Are there any apps that replace the camera app with something like this?  Maybe pops up a question that asks "do you want to take a real photo or load an image instead?" and does the appropriate action?

As far as I can tell these apps just open the default camera app which then takes a photo and returns the photo's filename to the calling app which can use the photo as necessary.