Marrying fixed line telecommunications with mobile services

Every fixed line operator, nearly all around the world, is faced with declining numbers of subscribers. Subscribers that quickly move to mobile subscribers. Various measures have been applied to make the fixed line business more attractive, such as SMS via fixed line - not realising, that the beauty of SMS is that you can do it on the run, and that the target group of SMS via fixed line is pretty small.
KT Corp, the largest telecommunications company in Korea is now trying something interesting to keep its subscribers of all segments in the ICT industry - Internet, fixed line, and mobile. The company has been granted a license by the government for a "One-Phone" service, effectively allowing customers to use both, fixed-line and mobile phones with one device. It basically works like a call forwarding function in the manner that an inbound fixed line phone call will transit automatically to a mobile handset when the user is inside the house or the office. While this is still somewhat inconvenient, it is a begin. How about one number, as one step further, for both fixed line and mobile?