I know you can control your phone via PC using bluetooth and the other way round. Therefore, it is possible to use your phone through another phone. That is, for example, to take photos manually without touching the camera phone. I haven't found any software to do this, but I may have been looking in the wrong place.
I'm using N95 and I'm hoping, if such software exists, I could use my N70 as the remote control.
Also, I've been looking for some kind of a macro software that allows you to record a "keyboard macro" for the phone. I've read about PyS60 and mShell, but I believe they don't allow you to script all setting changes, for example, the N95's camera exposure compensation.