docs: add FEAT-17 — Android Auto media-template live telemetry idea

FEATURES.md

@@ -36,6 +36,7 @@ dedicated PLAN.md phase (or fold it into the relevant existing work) and mark it
 | FEAT-14 | `SHIPPED` | Second T3U to replace onboard wlan0 (dual AC radios) | Phase 29 |
 | FEAT-15 | `SHIPPED` | Clear DTC codes from the DTC page | Phase 29 |
 | FEAT-16 | `SHIPPED` | Max-speed marker on trip replay map | Phase 29 |
+| FEAT-17 | `IDEA` | Android Auto media-template live telemetry (speed/RPM in now-playing) | unassigned |
 
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@@ -302,3 +303,30 @@ dedicated PLAN.md phase (or fold it into the relevant existing work) and mark it
   `max_speed_kmh`. Works identically on the Pi and the server portal (shared `history.js`).
 
 
+### FEAT-17 — Android Auto media-template live telemetry (speed/RPM in now-playing)
+- **Status**: `IDEA`
+- **Area**: Android app (`android/`) — new AA `CarAppService` + media-template `Session`
+- **Phase**: unassigned (Phase 28.x candidate)
+- **Requested**: owner — wants live RPM + OBD speed visible on the portable CarPlay/Android
+  Auto screen, without a separate app (the screen only runs CarPlay/AA, no Android).
+- **Idea**: register the yaris-obd app as an Android Auto **media** app (Fermata Auto /
+  OBD2AA style) and push live values into the "now playing" fields — e.g. title `87 km/h`,
+  subtitle `RPM 2400 · Coolant 90°C`, refreshed every 1–2 s from the Pi's `/api/obd/status`
+  (or a new lightweight endpoint). The phone keeps the full Compose app; the AA surface is a
+  separate templated screen (one APK, two surfaces).
+- **Constraints / risks**:
+  - **No gauges in AA** — only templated text/buttons; this is a text readout, not a gauge
+    cluster.
+  - **WiFi conflict** — wireless AA occupies 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 a gauge
+    app) or a whitelist patch (`aa-rs`/root/ADB); AAAD only installs its own fixed list and
+    Google patches these routes regularly.
+  - **Driving restrictions** — AA is templated and driver-safety-limited; best treated as a
+    parked/glance readout.
+- **Outstanding considerations**: ship as an AA mode of the existing app vs a standalone build;
+  whether the screen supports wired AA; whether the data path should be Pi-hotspot (wired AA)
+  or server (cellular).
+
+