I did some playing with a truck I was working on, the module I used came from a 91 c3500, but I found there were actually 4 functions you could use from the remote. Lock, unlock and 2 that weren't being used. Holding the unlock button added one and holding the lock and unlock at the same time was another.
I used it with some relays to make a remote start system with the factory key fob. Holding both buttons would start it and holding the unlock button would shut it back off. I also had it die if someone pressed the brake without inserting the key. I never thought about increasing the range though.