In the template:
Add a button to your form.
Set the button type to be "Webcam".
On the "On click" tab, set the Action to "Switch Camera".
In server-side code:
p_web.script('$("#somefield-camera").ntcam("switch")')
In JavaScript code
$("#somefield-camera").ntcam("switch");
You can also force a specific camera by setting the parameter to "user" or "environment". As in
p_web.script('$("#somefield-camera").ntcam("switch","user")')
$("#somefield-camera").ntcam("switch","environment");
Cheers
Bruce