What's a Bluetooth Gateway?

I'm thinking about dropping the phone service and buying a Bluetooth Gateway like this "Cell2Tel" one, when my current FIOS package expires.

From the Cell2Tel site:

easily combine your land line service (VoIP, traditional or cable company) and home or small office telephone system with up to two Bluetooth™ mobile phones. You can even cancel your home phone service completely

http://www.cell2telgateway.com/ [cell2telgateway.com]

Also available on Amazon.com for a little less $.