If it's wireless it's not a landline. Are you talking about a cordless home phone? Something like a 900 mhz one where the base station is located inside your home?
There isn't really a way to get it to work in your car as I believe it requires an AC power source and has a roam restriction so it can't use any towers except those in the very immediate area of your home.
Now picture your same home phone without thqat beige cord plugging into the wall, and instead with an internal antenna picking up a cellular signal. So it's like your cell phone you carry in your pocket or on your belt, but it's a home phone. I've never seen a tellular unit myself but I believe they're not much bigger than your normal cordless bases.
Did that answer your question sort of?
Yo what up?
Not much man. I'm talking to you in my car on my new SWEET 900 mhz phone!
They have an Ericsson F221m Wireless Landline at www.powertec.com.au which you can connect a landline phone, fax machine or laptop to.
I have one set up in my car with an external antenna, works great!