Virtual instruments are the mobile software designed to help users navigate, measure hidden environmental properties, or support various user interactions in a virtual environment. Over the past few years, we have developed several virtual instruments for educational virtual environments. However, the process of constructing virtual instruments is often difficult and time consuming because it requires the developers to understand not only the virtual reality systems but also mobile computing platforms. In this paper, we Int identify a few requirements for the development of virtual instruments. Then, we introduce the VIST (Virtual Instrument Scripting Toolkit), specifically designed for reducing the effort of designing virtual instruments. Finally, we will illustrate some applications of using VIST and then discuss the future research directions.