The first reviews of the iPod touch have cited some differences compared to Apple's similar iPhone. One of the biggest criticisms of the iPod touch was that it did not have the iPhone's email, mapping and stock tracking applications. Another complaint mentioned that the iPod touch had no physical buttons for volume control - a feature that the iPhone had. The iPod touch instead used software-based controls, which makes users to double click the home button, bringing up an on-screen volume control. The iPod touch also did not have the iPhone's external speakers, built-in camera, and Bluetooth capability, but the 2nd generation onward has external speakers and the Bluetooth capability. The fourth generation, released in September 2010, was the first iPod touch to feature the retina display and two built-in cameras for FaceTime and for videos and still photos. At least one critic has suggested that Apple may have left out these applications and hardware features on purpose in order to differentiate the iPod touch from its more expensive cousin, the iPhone. Others say that the touch does not need the applications mentioned above because it's an "iPod" and not a mobile phone. However, the 2009 model of the iPod touch does feature Bluetooth, but only to link with bluetooth headphones.