IF your key has the chip, you will have to have a spare key programmed for your Jeep. This can be a blank off of Ebay. Then this key has to be put in the bypass box. This lets the computer read the key to bypass the starter key in the onboard security system.
IF you don't have the chip key (and I don't), then you can install an aftermarket starter without the extra key. However, you might want to look at a security system with the integrated start function. Cost won't be much higher, if any, and installation won't be much more involved.
I am looking at this myself. I just have a hard time justifying it since i keep my Libby in a garage. It would help to have it warm at work for the trip home though.
Another thing to keep in mind though is that they can be illegal. Here in my area there is a law against leaving a car running without a driver in it. I know that sounds stupid, but there was a news segment on people getting tickets because their car was in the driveway warming up while they were in their house. The insurance companies are pushing it for theft reasons. They specifically asked about remote starter systems and the police said that the law didn't specify any exceptions so that they would be tickted.
Go government and Corporations! Yay!
Rescu2000
Also, autotoys has a remote starter with keyless entry (crimestopper) for $67 and a security system with remote start and 2-way remotes for $82 that will work two cars from the same 4 button remote.