CursorSubject is a Reactive Extension version of Android's CursorLoader. Handles retrieving the Cursor in a background thread, sending the result Cursor on the main thread, and resending a Cursor whenever the content changed notification is triggered.

CursorSubject.java

package com.example.models;

import android.database.ContentObserver;
import android.database.Cursor;
import android.os.Handler;
import android.os.Looper;

import java.io.Closeable;
import java.util.concurrent.atomic.AtomicReference;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.ParametersAreNonnullByDefault;

import rx.Observer;
import rx.Scheduler;
import rx.Subscription;
import rx.subjects.PublishSubject;
import rx.subscriptions.Subscriptions;
import rx.util.functions.Action0;
import rx.util.functions.Action1;
import rx.util.functions.Func2;

@ParametersAreNonnullByDefault
public abstract class CursorSubject implements Closeable {

  public CursorSubject(Scheduler execute_on, final Scheduler observe_on) {
    _last_cursor = new AtomicReference<>();
    _cursor_channel = PublishSubject.create();
    _execution_scheduler = execute_on;
    _load_cursor_action = new Action0() {

        @Override public void call() {
          try {
            final Cursor cursor = _cursor_retriever.retrieveCursor();
            if (cursor != null) {
              try {
                // Ensure the cursor window is filled.
                cursor.getCount();
                cursor.registerContentObserver(_content_observer);
              } catch (RuntimeException exception) {
                cursor.close();
                throw exception;
              }
              // Delivers resulting Cursor over Cursor channel
              observe_on.schedule(cursor, _deliver_cursor_action);
            }
          } catch (Exception exception) {
            _cursor_channel.onError(exception);
          }
        }
    };
    // Should make sure that the cursor is scheduled to be closed after the new one has been received
    _deliver_cursor_action = new Func2<Scheduler, Cursor, Subscription>() {

        @Override public Subscription call(Scheduler scheduler, Cursor cursor) {
            _cursor_channel.onNext(cursor);
            updateLastCursor(cursor);
            return Subscriptions.empty();
        }
    };
    // Schedules the first cursor retrieval (subsequent retrievals occur when content changes)
    loadCursor();
  }

/* Public API */
  public Subscription subscribe(Observer<? super Cursor> observer) {
    return _cursor_channel.subscribe(observer);
  }

  public Subscription subscribe(Action1<? super Cursor> on_next) {
    return _cursor_channel.subscribe(on_next);
  }

  /**
   * Retrieves the {@link android.database.Cursor}.
   */
  @Nullable protected abstract Cursor retrieveCursor();

/* Closeable */
  @Override public void close() {
    _cursor_channel.onCompleted();
    updateLastCursor(null);
  }

  /* package */void updateLastCursor(@Nullable Cursor cursor) {
    // Makes sure to close cursor
    final Cursor last_cursor = _last_cursor.getAndSet(cursor);
    if (last_cursor != null) last_cursor.close();
  }

  /* package */void loadCursor() {
    // Schedules Cursor loading on execution scheduler
    _execution_scheduler.schedule(_load_cursor_action);
  }

  /**
   * An implementation of a ContentObserver that takes care of connecting
   * it to re-load the data when the observer is told it has changed.
   */
   private final class ForceLoadContentObserver extends ContentObserver {

    public ForceLoadContentObserver() {
      super(new Handler(Looper.myLooper()));
    }

    @Override public boolean deliverSelfNotifications() {
      return true;
    }

    @Override public void onChange(boolean _) {
      loadCursor();
    }
  }

  private final Scheduler _execution_scheduler;
  /* package */final Action0 _load_cursor_action;
  /* package */final Func2<? super Scheduler, ? super Cursor, ? extends Subscription> _deliver_cursor_action;
  /* package */final AtomicReference<Cursor> _last_cursor;
  /* package */final PublishSubject<Cursor> _cursor_channel;
  /* package */final ForceLoadContentObserver _content_observer = new ForceLoadContentObserver();
}

ExampleActivity.java

package com.example;

import android.app.ListActivity;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.widget.CursorAdapter;
import android.widget.SimpleCursorAdapter;

import com.example.models.CursorSubject;

import rx.Observer;

import static rx.schedulers.Schedulers.io;
import static rx.android.schedulers.AndroidSchedulers.mainThread;

public class ExampleActivity extends ListActivity implements Observer<Cursor> {

/* Activity callbacks */
    @Override protected onCreate(Bundle _) {
      new CursorSubject(io(), mainThread()) {

          @Override
          @Nullable public Cursor retrieveCursor() {
            return getContentResolver().query(Uri.EMPTY, null, null, null, null);; 
    }.subscribe(this);

/* Cursor Observer */
    @Override public void onNext(Cursor cursor) {
        if (cursor.isClosed()) return;

        final CursorAdapter adapter = (CursorAdapter) getListAdapter();
        if (adapter != null) adapter.swapCursor(cursor);
        else setListAdapter(new SimpleCursorAdapter(this, android.R.layout.simple_list_item_1, cursor));
    }
    
    @Override public void onCompleted() { }

    @Override public void onError(Throwable _) { }
}