Why not use the Gemini flash voice-api directly instead? Cost?
I ask because from the demo, the tutor's voice seems mechanical.
I've played with the gemini voice api and it's quite impressive for conversation with low latency, I'd say perfect for your use case. It even switches languages if I say "Okay, let's talk in $foo language".
The vocabulary tooling looks neat and well thought out.
The vocabulary tooling looks neat and well thought out.