Property.java

import rx.Observable;
import rx.subjects.PublishSubject;

public class Property<T> {

  private T value;
  private PublishSubject<T> property;

  public Property() {
    property = PublishSubject.create();
  }

  public T getValue() {
    return value;
  }

  public void setValue(T value) {
    this.value = value;
    property.onNext(value);
  }

  public Observable<T> observe() {
    return property.asObservable();
  }

}

PropertySample.java

import rx.Observable;

public class PropertySample {

  public static void main(String[] args) {
    Property<String> property = new Property<>();

    property.observe().subscribe(System.out::println);

    property.setValue("New Value from Setter");

    Observable.just("New Value from Observable")
        .subscribe(property::setValue);

    System.out.println("Current val=" + property.getValue());
  }

}