Yep that's it, just with a different remote. The one I have is this one on ebay. Have a look through RightClick's stuff too, its usually the same black box but with different remotes (some are 10% off at the mo too). I'm adding mine to my gen 5 for the exact same reason as you There are cheaper options on ebay, some less than a tenner but I've used the RightClick one before and I thought paying a bit extra would be worth it.
As for the extra features, yep, just dont connect them up. If the gen 4s are similar to the 5s and you only want the remote locking feature, you can actually just utilise the wiring inside the door as shown here