Hi,
These should and do exist. Personally, I know that VXI makes a Gateway unit that works with thier own BT headset. (
http://vxicorp.com/storefront/pc-167...ott-b100.aspx). I'm sure other companies make similar units. The problem is, being able to buy just the Gateway (the part that interfaces with the landline).
In theory, you could buy a unit like that VXI Gateway, and instead of using thier headset (which is kind of bulky), you could pair it to your Jawbone. But that seems a little expensive for what you really need.
I guess my point is that there are units like what you need out there...it's just a matter of finding someone who can sell you just the Gateway.