Hello Walter,
The problem is "getUserMedia" it's not very well supported at this time. In particular Internet Explorer doesn't support "getUserMedia", and for that cause you cannot go working in App Builder, because they use Internet Explorer for their debugger.
I investigate about this in the past and the problem is to choice the right API in order to provide a way to "make a photo", for example, in almost all platforms. The problem of course is this "perfect API" doesn't exists at this time.
A possible solution is to use the Phonegap Camera plugin, however, if we use this in some control or action in App Builder, there is the first time that a control or action can works ONLY in certain platforms, and not in all.
Even when this can represent a problem, probably we need to take this solution until a pure Javascript API are supported by all the mobile and desktop browsers, but, until this plugin can be easily used from App Builder, what we can do?
I am updated App Builder right now to enhance the File input control in order to allow us to use the Capture attribute and the Accept attribute. Then I add the Capture, the Accept and also I add a new Url variable to the Input control.
The Capture attribute is not perfect because they do not work at this time in all platforms, but in the Android version of the Chrome browser, for example, they allow us to take a photo in a very similar way than the Phonegap Camera plugin, even better.
I add a new app sample named "ImagePick" that show how to use these new variables, for example, how to use the new Url variable in order to show the user selected (or taken) image into an Image control.
So until the Phonegap Camera plugin can be integrated in App Builder, take a look at the refered sample, Walter, because probably this can work more or less that you wanted. If you have Phonegap installed (I hope yes) try to compile an try this sample.
In fact I can't try the sample in my Android device, because, my specific Android version doesn't allow Input files at all... a controversial change in Android 4.4.2 that the community report as a bug and apparently Google fix in later Android versions...
Welcome to the world of cross browser and cross platforms development! :)