Book excerpt: Paying with mobile devices such as mobile phones or smart phones will expand worldwide in the coming years. This development provides opportunities for various industries (banking, telecommunications, credit card business, manufacturers, suppliers, retail) and for consumers. The book comprehensively describes current status, trends and critical aspects of successful mobile payment. It combines theory and practice. Comprising essential aspects of a successful mobile payment as well as successful case studies and practical examples, this book is for all who are developing, offering and using mobile payment.