You have to start with a render from the point of view of whatever it is that you want to be reflective.  Then you can take your object, go to uv face select mode and open a uv editor, set up your uv coordinates if necessary and load the reflection render, then in the uv editor panel go to image->real time texture mapping and select reflection instead of uv coordinates :)  It's been around for a while, I believe it used to be the only way of getting reflection in the internal renderer.