Voice-Controlled Android AI Assistant Development

Hello,
I am looking to develop a Voice-Controlled Android AI Assistant App with advanced hands-free mobile control features.
Project Overview:
I want to build an assistant that can:
• Custom wake word activation
• Hindi + English voice recognition
• Open installed apps via voice
• Perform basic in-app actions using Accessibility Service (scroll, tap, back)
• YouTube search & play via voice
• Send WhatsApp messages via voice
Backend Requirements:
• Firebase backend integration
• User authentication (Email/Phone)
• Premium subscription system (Monthly plan)
• User database
• Push notifications
• Usage analytics
Admin Panel (Web Based):
• Secure admin login
• View registered users
• Activate/Deactivate premium
• Revenue dashboard
• Send notifications
• Manage command database
Please share:
Your experience with similar Android + Firebase projects
Estimated cost
Development timeline
Technology stack
Whether you have worked with Accessibility Service before
I prefer milestone-based payment and long-term collaboration.
Looking forward to your response.
Thank you. Md Salman