Well, if you want to use DEI which is what I believe is the best, you could actually use almost any of their lines. THey all have aux. input activations. The ones that are kinda setup for this is the Valet 561r units. You'd set it up to activate when you press the lock button 3 times.
Personally, I wouldn't do it because the range of your OEM remotes is only about 75' at best while the cheapest DEI one is about 500'.
As far as bypasses, I would use the DEI part# 555L for the passlock 2 system your truck would have if it's a '02 and older. If you have a '03 to '05, I would get the combo bypass from
www.bypasskits.com They have one that does all kinds of things like bypassing PK2, keyless, horn, lights, and owner #1 reconition.