Generally speaking, the main idea of the RadToolTip control is to show up when the user hovers over something so the functionality that you require is in some way out of the scope of the control. Nevertheless I logged your suggestion in our database and we will consider it for a future version.
For now, I would suggest to check the RadWindow control which has a full-blown API for showing and positioning. With Q2 at the end of the summer, the RadWindow control will also be ported to the Prometheus suite which will give you even more flexibility in its usage.
the Telerik team