RxUtils.java

public static <T> Observable<T> toObservable(@NonNull final ObservableField<T> observableField) {
    return Observable.create(new Observable.OnSubscribe<T>() {
        @Override
        public void call(final Subscriber<? super T> subscriber) {

            if (!subscriber.isUnsubscribed()) {
                subscriber.onNext(observableField.get());
            }

            final OnPropertyChangedCallback callback = new OnPropertyChangedCallback() {
                @Override
                public void onPropertyChanged(android.databinding.Observable dataBindingObservable, int propertyId) {
                    if (dataBindingObservable == observableField) {
                        subscriber.onNext(observableField.get());
                    }
                }
            };

            observableField.addOnPropertyChangedCallback(callback);

            subscriber.add(Subscriptions.create(new Action0() {
                @Override
                public void call() {
                    observableField.removeOnPropertyChangedCallback(callback);
                }
            }));
        }
    });
}