[Shop-talk] True "keyless" entry add on

[eric at megageek.com]

OK, I bought a new (to me) GMC Envoy XUV.  It's a very versatile truck and 
I'm really digging it. 

I've spent a few days adding my "touches" to it, but there is one thing 
that eludes me, and I was hoping if maybe a car guy here would have the 
answer.

My old Ford explorer had a true "keyless" entry system.  This means that 
it had a number pad on the door and you could unlock the door by putting 
the code in.

Does anyone know if an aftermarket system like this exists?  When I do my 
searches, I only come up with systems that use a remote transmitter to 
open the door.

Here is my thinking, it shouldn't be hard to make this add on.  If you 
have a key pad that has constant power, all it would need is a relay to 
the electric door lock wires.

OR, could I get a system out of a Ford in the junk yard and add it myself?

Any help would be appreciated.

Thanks.

Eric P
"Be as beneficent as the sun or the sea, but if your rights as a rational 
being are trenched on, die on the first inch of your territory." Ralph 
Waldo Emerson