Add README for data API.

README.md

@@ -30,10 +30,10 @@ _OpenTracks_ is a sport tracking application that completely respects your priva
 ## Features:
 * __Tracking:__ track your sport and outdoor activities 
 * __Photos and Markers:__ mark interesting locations while tracking (also with photos)
-* __Heart rate:__ supports bluetooth LE sensors
+* __Heart rate:__ supports Bluetooth LE sensors
 * __Export data:__ export tracks either as KMZ (incl. photos), KML or GPX
 * __No Internet access:__ Internet is not used
-* __Voice annoucements__
+* __Voice announcements__
 * __No advertising__
 * __Privacy:__
     * _does not contain any in-app analytics_
@@ -47,6 +47,9 @@ _Please note:_
 _Tracks_ does not contain a _map_ (as this would required Internet access).
 To show your tracks on a map, a 3rd party application (e.g., [OsmAnd](https://play.google.com/store/apps/details?id=net.osmand) or [MAPS.ME](https://play.google.com/store/apps/details?id=com.mapswithme.maps.pro)) needs to be installed.  
 
+## Custom Dashboards
+As of v3.3.1 OpenTracks enables to use custom dashboards.
+The reference implementation is [OSMDashboard](https://github.com/OpenTracksApp/OSMDashboard), which presents an OpenStreetMap map (showing the current track, incl. updates).
 
 ## Screenshots
 <div>

README_DEVELOPER.md

@@ -0,0 +1,30 @@
+# OpenTracks Data API
+
+## Reason
+OpenTracks by itself only provides basic features for data visualization and also lacks functionality for analytics.
+By itself OpenTracks provides a basic dashboard that can show summary of a track (while recording as well as afterwards).
+Although this might be (mostly) sufficient, it has some limitations.
+This include limited configurability (e.g., ordering of shown elements) and the lack of Internet access.
+In fact, the later is considered a feature but severely limits the implementation presenting a map (at least in an easy way). 
+
+_NOTE:_ for showing a track on a map a workaround was implemented in OpenTracks.
+Data could be exported as KMZ and presented in 3rd-party application (e.g., [OsmAnd](https://play.google.com/store/apps/details?id=net.osmand) or [MAPS.ME](https://play.google.com/store/apps/details?id=com.mapswithme.maps.pro)). 
+
+For the time being, the OpenTracks Data API can be used to implement mainly custom dashboards.
+
+## Implementation
+OpenTracks by default does not expose any data to 3rd-party applications.
+On the request of the user (i.e., pressing a button), an Intent is created that exposes the `Track` data (it's summary) as well as the `TrackPoint`s.
+For each, one URI is provided.
+These URIs notify observers if on content changes (e.g., a new `TrackPoint` was added).
+
+Limitations:
+* only tracks selected by the user is exposed,
+* `Waypoints` are not exposed,
+* access is only granted temporarily and automatically revoked (see `FLAG_GRANT_READ_URI_PERMISSION`),
+* no write access is impossible, and
+* neither track recordings can be started, paused, or stopped.
+
+All required information can be found in `IntentDashboardUtils.java`. 
+
+A _reference implementation_ is the [OSMDashboard](https://github.com/OpenTracksApp/OSMDashboard).