Integrated development environments are essential for efficient realization of complex industrial products, typically consisting of both software and hardware components. Powerful equation-based object-oriented (EOO) languages such as Modelica are successfully used for modeling and virtual prototyping increasingly complex physical systems and components, whereas software modeling approaches like UML, especially in the form of domain specific language subsets, are increasingly used for software systems modeling. A research hypothesis investigated to some extent in this thesis is if EOO languages can be successfully generalized also to support software modeling, thus addressing whole product modeling, and if integrated environments for such a generalized EOO language tool support can be created and effectively used on real-sized applications. However, creating advanced development environments is still a resource-consuming error-prone process that is largely manual. One rather successful approach is to have a general framework kernel, and use meta-modeling and meta-programming techniques to provide tool support for specific languages. Thus, the main goal of this research is the development of a meta-modeling approach and its associated meta-programming methods for the synthesis of model-driven product development environments that includes support for modeling and simulation. Such environments include components like model editors, compilers, debuggers and simulators. This thesis presents several contributions towards this vision in the context of EOO languages, primarily the Modelica language. Existing state-of-the art tools supporting EOO languages typically do not satisfy all user requirements with regards to analysis, management, querying, transformation, and configuration of models. Moreover, tools such as model-compilers tend to become large and monolithic. If instead it would be possible to model desired tool extensions with meta-modeling and meta-programming, within the application models themselves, the kernel tool could be made smaller, and better extensibility, modularity and flexibility could be achieved. We argue that such user requirements could be satisfied if the equation-based object-oriented languages are extended with meta-modeling and meta-programming. This thesis presents a new language that unifies EOO languages with term pattern matching and transformation typically found in functional and logic programming languages. The development, implementation, and performance of the unified language are also presented. The increased ease of use, the high abstraction, and the expressivity of the unified language are very attractive properties. However, these properties come with the drawback that programming and modeling errors are often hard to find. To overcome these issues, several methods and integrated frameworks for run-time debugging of the unified language have been designed, analyzed, implemented, and evaluated on non-trivial industrial applications. To fully support development using the unified language, an integrated model-driven development environment based on the Eclipse platform is proposed, designed, implemented, and used extensively. The development environment integrates advanced textual modeling, code browsing, debugging, etc. Graphical modeling is also supported by the development environment based on a proposed ModelicaML Modelica/UML/SysML profile. Finally, serialization, composition, and transformation operations on models are investigated.