Question: I want a chatbot that can understand voice commands and respond accordingly - does such a service exist?

The best of the bunch is Retell AI. The service lets developers build conversational Voice AI with a human-like tone and a response time of about 800ms. It can handle multiple languages, voices and voice cloning, and has features like complex workflow setup, deployment across multiple channels and sentiment analysis. It's designed to scale and to be secure, with HIPAA compliance and SOC certifications. It's pay-as-you-go pricing means you can use it for whatever you need.

Another good option is ZeroBot. The AI-powered chatbot lets you converse with trained agents like Tutors, Counselors and Doctors by voice. The service uses the Groq LPU Inference Engine for high-performance conversations and offers a range of AI agents for different purposes. That means your interactions will be natural and immediate, and the service can be used for a variety of tasks.

If you want to build your own voice AI platform, SoundHound has tools to help you do so. It offers features like branded wake words, automatic speech recognition and natural language understanding. With its Houndify developer platform, companies can create and deploy conversational assistants that can help users and deliver insights into what they're doing.

Last is boost.ai, an enterprise-focused conversational AI service designed to boost customer satisfaction and automate customer service. It uses AI chat and voice bots for personalization and can handle high traffic volumes without high costs. It can be easily integrated with existing systems and offers a hybrid approach that combines human and virtual agents.