docs: move Android Auto media-template telemetry idea into poc mediacenter plan

poc/yaris-mediacenter-plan.md

@@ -290,6 +290,37 @@ Add M6 later as an optimization for Spotify specifically.
 
 ---
 
+### Phase M7: Android Auto "now playing" telemetry readout (stretch goal)
+**Goal:** Show live OBD values (speed, RPM, coolant) on the portable CarPlay/Android Auto
+screen. The 9.26" display only runs CarPlay/AA — it has no Android app surface — so the only
+viable path is a templated AA app that spoofs media metadata (the "now playing field" trick).
+
+- [ ] Register the yaris-obd Android app as an Android Auto **media** app
+      (`CarAppService` + `MediaSession`) — Fermata Auto / OBD2AA style.
+- [ ] Push live values into the now-playing fields, refreshed every 1–2 s from the Pi's
+      `/api/obd/status` (or a new lightweight endpoint):
+      - Title: `87 km/h`
+      - Subtitle: `RPM 2400 · Coolant 90°C`
+- [ ] One APK, two surfaces: the full Compose app stays on the phone; the AA surface is a
+      separate templated screen.
+
+**Constraints:**
+- **No gauges** — AA only exposes templated text/buttons; this is a text readout, not a
+  gauge cluster.
+- **WiFi conflict** — wireless AA owns the phone's WiFi, so it can't also be on the Pi
+  hotspot. Requires **wired AA** (USB) so WiFi stays free for the Pi, or real-time OBD
+  pushed via the server over cellular (adds latency + load).
+- **Distribution** — custom AA apps need Google Play review (unlikely to approve) or a
+  whitelist patch (`aa-rs`/root/ADB); AAAD only installs its fixed list and Google patches
+  these routes regularly.
+- **Driver safety** — AA is templated and driver-safety-limited; treat as a parked/glance
+  readout.
+
+**Note:** this phase is Android-side (lives in `android/`), unlike M1-M6 which are
+Pi-side. It lands under the same "media center" umbrella the car converges on.
+
+---
+
 ## Hardware Status
 
 | Component | Status |