Hello @やまたく,
Yes, you can mirror an Android Phone to the Google TV Streamer. There are a couple was to do this. On your Android phone look for Cast Screen in your Quick Settings in the Notification Bar drop down.
You can also find it by long pressing on the Google TV Streamer in the Google Home app and you should see a Cast my screen option.
I'm not sure on the quality but it is reduced from what your screen displays.
When done morning your screen, look for the Stop casting option in your Notifications.
Let me know if you have further questions.
Brett
