Even with an iPhone 4, a shallow depth of field is possible.
Tip: When using your iPhone camera, tap on the screen where the subject is you want to focus on. In this case, I put the camera close to the bottle, tapped on the pyramid logo, and made sure I had another subject in the background that stands out, i.e. the blue shirt and red hat that matches the logo of the bottle. Focusing on the bottle while putting the camera close to the bottle makes the subject 4 feet in the background a bit out of focus.