Recently, the popularity of mobile smart phones has fostered the development of a variety of mobile Mashup applications. A mobile Mashup application retrieves and glues together resources on the Web to create a new service. Compared with mobile Web browsers, mobile Mashup applications provide users with fancy GUIs and specialized services. Thus, mobile Mashup applications have become a significant role on mobile phones. Due to low-bandwidth wireless links and limited battery capacity, a large number of transmissions of mobile applications is prohibitive. However, because mobile clients mainly use mobile Web browsers to access the Web, prior work only focused on reducing the data sent to mobile Web browsers. In this paper, we present a proxy system as well as several techniques to reduce the volume of transmissions sent from and received by mobile Mashup applications based on the observations on characteristics of RESTful APIs. We propose an API query language (AQL), which enables mobile applications to batch multiple RESTful API method calls into one single query, thereby reducing the number of HTTP requests and responses. In addition, we employ an image multi-get module and Gzip compression module for image and text transmission reduction, respectively. The experimental results show that the proposed system and techniques effectively reduces the number of HTTP requests and responses and sizes of packets.