Even tough you cant use Free Plan on anything else than your personal projects, its still a perfect way to try and learn SDK of VirtualGSMS. It has some limitations too. You can learn more at Plans section.
Latest and second Shield on VGSMS is GeminiVisionAPI - which gives an eye to your simple microcontroller projects. It supports custom API keys and custom prompts to send to Gemini 1.5 Flash. You can read more in this article.