I do not think it exists yet (though Panasonic has come close), but perhaps I am wrong. I was looking to see if a cordless home telephone yet existed that allowed not only a landline connection for regular telephone use, but also bluetooth connections simultaneously to multiple cellular telephones.

From a practical standpoint, this would allow a home telephone, and also allow family members to leave their cell phones (likely near the base I would assume) and also allow their cellular telephones to ring on the house telephone.

Also–I do imagine this exists with business systems, that are likely very expensive. My question is really whether residential versions have been developed yet.