Our oldest is 5 (or will be on Thursday) and she slept with us until this last summer. She had a fibral seizure when she was about 8 months old and scared us to death.
We worked really hard to get the bedroom together - we also have another daughter who will be 2 in November. We finally on a Thursday night told her that "tonight you'll sleep with us, and starting tomorrow, you'll get to sleep in your own special bedroom!" and made it sound exciting. She never looked back and has done an awesome job. Part of it was that we also had our youngest in her crib in the room too.
I've seen Supernanny and "Take Home Nanny" do a couple things that seemed to work well. One was to have a chair in the room (to reassure them your still around), but set it in such a way so that when you're sitting in it you aren't looking at them. Whenever they get up, go over and put them back in the bed without saying anything. Keep doing this until they fall asleep. It took one mom about 2 hours and several several times of putting the child back in bed before the child (a boy) went to sleep. But it worked. For the older children it was to put them in bed, tell them it's time for bed, then leave the room. Every time the child came back out, the parent put them back in bed until they finally went to sleep.
For whatever it's worth....
Good luck!