Mobile phone to integrate with home line

Try this:

http://home.singtel.com/mio/ 

If you are still interested in an answer, you don't really need any hardware to integrate the cell phone with home phone. What you need is a service from Phone.com.  Using the www.phone.com service you can in fact make the two phones ring at once, and then pick up any one of them. Here is what i have done. I have transferred my home phone number to Phone.com. I also got a VoIP home phone from them. Now using the web, I set up the service to ring both my new home phone and my cell phone when a someone calls my original home phone number. I disabled my cell phone Voice mail and did transfer on busy or no answer to my Phone.com service so that I get all my voicemails in one place as well.

If this is not clear call their 24x7 support.