Apollo is a multi-model AI chat app for iPhone and iPad that provides instant access to leading AI engines like ChatGPT, Claude, and Gemini. It allows users to test, compare, and combine different LLMs seamlessly, with customizable prompts and settings. Ideal for developers, researchers, and AI enthusiasts, it supports various use cases including content creation, coding, translation, and data analysis. The app features a user-friendly interface, quick model switching, and the ability to save favorite responses.