OK, I'm going to borrow quite a bit of information from Vinny over at the MDX site. I've made this change on my MDX. The MDX, Pilot, and Ridgeline are all very similar vehicles. I believe many of the wires and locations will be the same, but since I don't have a Ridgeline to look at I can't tell you if things are exactly the same or not.
This conversion is based upon the DEI 452T Door Lock Pulse Generator. It's available in many locations, but here's one I know of (cost $7.99):
http://www.radiomancaraudio.com/detail.asp?PRODUCT_ID=DE452T
Here are the instructions for the module:
http://www.azcartoys.com/images/425T.PDF (note that you won't use most of the wires!)
Since I understand that the Ridgeline has the option to autolock all doors at 9MPH we don't need the 452T to do any locking of the doors. I'm told the Ridgeline will only unlock the drivers side door via the factory settings. We can fix that with the 452T. If connected as described you will unlock ALL doors when the ignition key is turned off.
The doorlock wires are behind the passenger side kick panel on the MDX... probably the same on the Ridgeline:
The power lock wire is black/orange and the unlock wire is blue/orange. You only want to unlock so only hook up the blue/orange.
Use the fuse box below for constant 12v and igition 12v. There is a bolt below the fusebox for ground. NOTE: Picture is not correct for Ridgeline install and module now looks different (much smaller). Must be true ignition 12v and not the delayed power that stays on until you open the door.
There's plenty of room behind the panel to keep the module and all wires hidden. NOTE that the actual wiring for the Ridgeline is not represented here, but the concept is the same.
The MDX and most likely the Ridgeline has negative pulse locks so other than power only the solid blue wire is used.
The entire procedure is very simple and probably not as complex as I've made it seem here!