Make and receive land line phone calls on my mac?

I have two phones, an iphone and a land line. I'm spending several hours a day on the phone. I know I can use my iphone and my mac working together, but I want to be able to do this with my landline too. * Headset on a 3.5 mm plug to my mac pro. (Do I need a splitter for mic and audio out?) * Call display showing the number in an app, that I can cut and paste into a call log. * Double click dialing. I *think* I need a USB or internal card modem for this.