Recent convergence of imaging sensors and general purpose processors on mobile phones creates an opportunity for a new class of augmented reality applications. Robust image feature extraction is a crucial enabler of this type of systems. In this article, we discuss an efficient mobile phone implementation of a state-of-the-art algorithm for computing robust image features called SURF. We implement several improvements to the basic algorithm that significantly improve its performance and reduce its memory footprint making the use of this algorithm on the mobile phone practical. Our prototype implementation has been applied to several practical applications such as image search, object recognition and augmented reality applications.