Near Field Communication's card emulation mode is a way to put virtual smart cards into mobile phones. A recently launched application is Google Wallet. Google Wallet turns a phone into a credit card, a prepaid card and a tool to collect gift certificates and discounts. Card emulation mode uses dedicated smart card chips, which are considered to fulfill high security standards. Therefore, card emulation mode is also considered to be safe and secure. However, an NFC-enabled mobile phone introduces a significantly different threat vector. Especially a mobile phone's permanent connectivity to a global network and the possibility to install arbitrary applications onto smart phones open up for several new attack scenarios. This paper gives an overview of the new risks imposed by mobile connectivity and untrusted mobile phone applications. The various APIs for secure element access on different mobile phone platforms and their access control mechanisms are analyzed. The security aspects of mobile phones are explained. Finally, two practical attack scenarios, a method to perform a denial of service (DoS) attack against a secure element and a method to remotely use the applications on a victims secure element without the victim's knowledge, are highlighted.