Object invisible to camera but shown in reflection

As the title suggests, I'm looking for a way to have an object which is only visible in reflections. Any ideas how I might do this?

Well... I'm not too sure about this... But if you have Unity Pro, perhaps you could try looking into Render Texture?

http://unity3d.com/support/documentation/Components/class-Camera.html

Since they mentioned you could put Camera views onto Gameobjects as textures... Perhaps you could do a certain sort of script which would make a camera on the mirror follow you when you passed by it, and render that view onto the mirror.

All cameras except for the camera on the mirror would be culled in such a manner that only the camera in the mirror can see that object.

Hopefully this would work?

Have your object on a layer that is not in the culling mask of the camera, but is in the culling mask of the reflection probe.

There, now that your question is answered you can finally finish your project from 11 years ago!