Observable String for two-way data binding, based on Fabio Collini's article and Frode Nilsen's gist. This version works without an extra id in the resources and with all TextViews.

TwoWayBoundString.java

import android.databinding.BaseObservable;
import android.databinding.BindingAdapter;
import android.databinding.BindingConversion;
import android.os.Parcel;
import android.os.Parcelable;
import android.text.Editable;
import android.text.TextWatcher;
import android.widget.TextView;

import java.io.Serializable;
import java.util.Collections;
import java.util.Set;
import java.util.WeakHashMap;

/**
 * An observable class that holds a String and is capable of two-way data binding with TextViews and
 * its descendants (e.g. EditText). To be used with Android's Data Binding Library.
 *
 * Based on:
 * - Fabio Collini's great blog article about two-way data binding
 * (https://medium.com/@fabioCollini/android-data-binding-f9f9d3afc761) and
 * - Frode Nilsen's implementation of TwoWayBoundString
 * (https://gist.github.com/Nilzor/05a7db14819d09e45262).
 *
 * This version works without defining an id in the resources and with all TextViews. It also
 * implements the Parcelable interface.
 * For EditTexts, the cursor is moved to the end after a value change in the model.
 *
 * For Android API version < 9, <code>Set<Object> mEmitters</code> must be replaced with e.g.
 * <code>Map<Object, Boolean> mEmitters</code>, because <code>Collections.newSetFromMap(...)</code>
 * is not available.
 *
 * @author Stefan Kleeschulte
 */
public class TwoWayBoundString extends BaseObservable implements TextWatcher, Parcelable, Serializable {
    static final long serialVersionUID = 1L;
    private String mValue;
    private Set<Object> mEmitters = Collections.newSetFromMap(new WeakHashMap<Object, Boolean>());

    /**
     * Creates a TwoWayBoundString with the given initial value.
     *
     * @param value the initial value for the TwoWayBoundString
     */
    public TwoWayBoundString(String value) {
        mValue = value;
    }

    /**
     * Creates a TwoWayBoundString with the initial value of <code>null</code>.
     */
    public TwoWayBoundString() {
    }

    /**
     * @return the stored value.
     */
    public String get() {
        return mValue;
    }

    /**
     * Set the stored value.
     */
    public void set(String value) {
        if (mValue == null && value == null) return;
        if (mValue == null || !mValue.equals(value)) {
            mValue = value;
            notifyChange();
        }
    }

    /**
     * Register this TwoWayBoundString instance as TextWatcher for the given TextView if it is not
     * already registered.
     *
     * @param textView the TextView to register on
     */
    public void registerTextWatcher(TextView textView) {
        if (!mEmitters.contains(textView)) {
            mEmitters.add(textView);
            textView.addTextChangedListener(this);
        }
    }

    /**
     * BindingAdapter enabling two-way-binding for <code>android:text</code> attributes (for
     * TextViews, including EditTexts): Updates TextView if TwoWayBoundString value changed and
     * registers TwoWayBoundString as TextWatcher for the TextView.
     *
     * @param textView the TextView to update
     * @param twoWayBoundString the TwoWayBoundString instance that changed and that shall be
     *                          notified about changes in the TextView
     */
    @BindingAdapter("android:text")
    public static void bindTextView(TextView textView, final TwoWayBoundString twoWayBoundString) {
        twoWayBoundString.registerTextWatcher(textView);

        String newValue = twoWayBoundString.get();
        if (!textView.getText().toString().equals(newValue)) {
            textView.setText(newValue);
            if (textView instanceof EditText) {
                ((EditText) textView).setSelection(textView.getText().length());
            }
        }
    }

    /**
     * BindingConversion enabling one-way binding for other attributes.
     *
     * @param twoWayBoundString the TwoWayBoundString instance that changed
     * @return plain String object
     */
    @BindingConversion
    public static String twoWayBoundStringToString(TwoWayBoundString twoWayBoundString) {
        return twoWayBoundString.get();
    }

    /**
     * TextWatcher interface.
     */
    @Override
    public void afterTextChanged(Editable s) {
    }

    /**
     * TextWatcher interface.
     */
    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
    }

    /**
     * TextWatcher interface - updates the value of this TwoWayBoundString instance when a bound
     * TextView's text changes.
     */
    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {
        this.set(s.toString());
    }

    /**
     * Parcelable interface.
     */
    @Override
    public int describeContents() {
        return 0;
    }

    /**
     * Parcelable interface.
     */
    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(mValue);
    }

    /**
     * Parcelable interface.
     */
    public static final Parcelable.Creator<TwoWayBoundString> CREATOR = new Parcelable.Creator<TwoWayBoundString>() {
        @Override
        public TwoWayBoundString createFromParcel(Parcel source) {
            return new TwoWayBoundString(source.readString());
        }

        @Override
        public TwoWayBoundString[] newArray(int size) {
            return new TwoWayBoundString[size];
        }
    };
}