Home Cell

A modern Cell handset provides many conveniences, such as caller ID, and an easy-to-use phone book. You'd like to use the tool even at home, but it's much cheaper to use the land line, and only burn minutes when away from home (or the office).

Either a cell phone which becomes a cordless phone when in the proximity of a cordless base station, or a very low-power cell site which operates only in your home, but routes the calls over your land line are the two approaches I see.