Base-stations that re-route calls made from your landline phones over your cellphone (making the most of your inclusive minutes) aren't new, but they tend to be expensive. The XLink BT Cellular Bluetooth Gateway actually comes in under a ton, however (by a wide margin no less) and can wirelessly connect to three different cellphones at once.
Both incoming and outgoing calls are supported, and if you get a better rate on one cellphone contract than the other (such as unlimited weekend calls) you can specify which line to call out from. The XLink automatically reconnects to handsets when they come into range, and can be linked to as many landline phones as you want. It also supports call-waiting (if, say, a second cellphone rings when you're on a call through the first) together with Caller ID.
Frankly, for $79.99 it seems a bargain. XLink also sell the BTTN gateway, which can connect to up to three cellphones plus a landline (or VoIP line), for $109.99.
[via Red Ferret Journal]