Mobile systems have used silicon for the root of security in the form of a Subscriber Interface Module (SIM) card for many years, this use is expanding to other mobile systems and in future other consumer devices. However the growth in mobile internet transactions is leading to new demands in silicon in the SIM and the handset to provide secure mobile solutions for payment, content management and multi-application systems. This paper will review the current status and identify the key issues for future and possible options.