Observable property allowing to add observers at runtime

Via Delegates.observable, Kotlin permits observable properties. I need, however, the ability of adding observers at runtime, as Java's Observable class does.

What I have now, is the following:

import java.util.*
import kotlin.reflect.KProperty
import kotlin.reflect.KProperty0
import kotlin.reflect.jvm.isAccessible


class MyObservable<T> (var v: T): java.util.Observable() {

    operator fun getValue(thisRef: Any, prop: KProperty<*>) = v
    operator fun setValue(thisRef: Any, prop: KProperty<*>, newValue: T) {
        v = newValue
        setChanged()
        notifyObservers()
    }
}

fun <T> addObserver(prop: KProperty0<T>, observerFn: (T) -> Unit) =
        (prop.apply{ isAccessible = true }.getDelegate() as MyObservable<T>)
                .addObserver(Observer({ o, _ -> observerFn((o as MyObservable<T>).v) }))


class ObservableExample {
    var i: Int by MyObservable(3)
}

fun main(args: Array<String>) {
    val ex: ObservableExample = ObservableExample();

    addObserver(ex::i, { println(it) })

    ex.i = 7
    ex.i = 9

    // prints:
    // 7
    // 9
}

It works, but it feels like reinventing the wheel.

Isn't there a standard solution for this?

If not, is what I've done correct?