Now that sims in coffins can do this I think it should be possible to add to normal beds. Note before they woohoo in the casket they kiss in the casket.
Also the casket is a single bed so maybe it could be possible to get this for single beds as well.
http://i293.photobucket.com/albums/mm68/sharkloverplayer_2008/Vampires/01-28-17_6-49-09nbspPM.png~original
http://i293.photobucket.com/albums/mm68/sharkloverplayer_2008/Vampires/01-28-17_6-50-54nbspPM.png~original
http://i293.photobucket.com/albums/mm68/sharkloverplayer_2008/Vampires/01-28-17_6-51-04nbspPM.png~original
