Currently in the RhoElements Runtime you will need to use the Imager API in order to take a picture: http://docs.rhomobile.com/rhoelements/imager/
Obviously this is confusing but in the next release (4.0) we will be unifying disjointed APIs like Camera and Imager into a single Camera API.
I hope this helps both now and for the future.
do you know if with the next release Camera and Barcode APIs will be available with RhoElements Runtime? When do you think will next release be ready?