Here's another option.
http://www.phonelabs.com/
I used the Dock 'n Talk a ways back with no problems at all. I had a 2 line Uniden cordless phone set, where my land line was Line 1 and my cell was Line 2. Dialing out is pretty seemless when compared to a land line, although they do suggest pressing # at the end of dialing but it is not required. With any of these options, I call your attention to the fact that you will need to keep the cell phone plugged in as there is your typical bluetooth battery drain.
It may be a little more expensive option but it is an option. Hope it helps.
gottago
Sprint Touch w/ WM 6.1