Just tried out Gemma 4 - E3B locally on my pixel phone. Using Google Edge Gallery with network permissions disabled (GrapheneOS)
It understands audio. Maybe image works too. Speed is decent. As long as prompts are simple and clear, i think its useful.
Not sure about battery consumption. But i bet for 80% of cases we dont need data center. It might not program but can tell u how to color SVG when u are offline.
