So I did some research, and ended up at AliExpress, the consumer portal for the big Chinese B2B site Alibaba. What I found was quite interesting; if you're willing to do a little research, you can obtain and install your own camera system for about $80, and install it in about 2 hours.
What you need are:
- A rear-view camera with wireless transmitter and receiver (otherwise you'll be stringing cable from your trunk to the front of the car). I found this one for $40 that is specifically made for the 2012-2013 Elantra. If you have a different car, you can find one that fits yours and adapt these instructions.
- A small LCD panel you can mount in the front of the car. There are zillions of them; I picked this one for $35 because it would fit nicely into the dashboard in the pocket which contained the cigar lighter socket and also had a suction mount, in case I changed my mind.
- A cigar lighter adapter plug that terminated in a standard jack. I happened to have one in my junk box. If you have one that doesn't have the right jack, you can just splice it directly into the LCD power connector. Make sure it's a basic one that isn't doing any voltage conversion!
- A couple of tap splices for grabbing power from the rear backup lights.
- Two pair of wire connectors of some sort.
- A Philipps screwdriver.
- Wirecutters and strippers.
- A soldering iron.
- A multimeter.
Here's my breadboard setup, using a 12v battery.
The center nipple on the cigar adapter is positive (+), and the springy things on the side are negative (-). To assemble the LCD screen and video receiver, you cut one of the wires coming out of the plug, strip both ends, and test it to see if it connects to the center nipple. If so, you twist the two ends together again, along with the red power wire from the receiver. If not, you twist them together with the black wire. If you get it right, when you apply 12v of power to the cigar adapter, the green light on the receiver will light up. The LCD screen may brighten a bit, but it won't show a picture unless the transmitter is on and sending something.
Solder the wires together and insulate them with tape, plug the cigar adapter plug into the red power plug of the LCD, and the receiver output into one of the video inputs (most of these LCDs have two inputs, it doesn't really matter which you use unless you also want to use the screen for other things).
When you're all done, you'll have something that looks like this:
Now out to the car. Pop open the trunk and take a look at the plastic bolts holding the top liner to the trunk lid. Unscrew them most of the way and then they pull right out. They consist of a central bolt and an outer flange. To replace them when you're all done, just unscrew them completely, squeeze the outer flange tabs a bit, insert it through the liner into the trunk lid, and push the bolt back in -- no screwing required!
You'll have to twist around to see the square cover that hides the hole where the camera goes. Just squeeze the tabs one at a time and wiggle and it'll come out. Remember to save it in case you need to restore the car to factory condition (such as at the end of a lease).
Here you can see the hole from the outside. When the trunk is closed, the hole is parallel to the ground.
The camera has two small tabs on one edge and a big spring-tab on the other edge. You just feed the wires through the hole and click the camera into place.
Now for the slightly tricky part. Find the connector that powers the white backup and red brake lights. It has 3 wires, black, green and blue. Remove it by squeezing a tab and pulling it gently -- a small pair of pliers makes this much easier, because it's in an awkward position.
Use your multimeter to figure out which wires feed the backup lights (not the brake lights!). These lights are on anytime the car is in reverse. On the Elantra, the blue wire is positive (+) and the black wire is negative (-). Check carefully; I got it wrong the first time, which is why I connected a red wire to the negative lead. Get a couple of short lengths of 14-gauge wire and use the tap splices to connect into the car's wires. Don't connect the transmitter power wires directly; they are too small and you may not get a good connection!
To use a tap splice, your new wire goes in the completely closed hole in the splice, and the existing wire slots into the half-open slot, then you push down on the metal tab with pliers.
Once you've done this, put connectors on the other ends of the wires, and also on the power wires coming from the transmitter.
Plug the transmitter into the camera (video and power), and connect it up to your new power wires. Then get someone to turn on the car and put it into reverse; you should see the power light on the transmitter come on.
If at this point you get run over, either you're an idiot or someone doesn't like you very much.
Now go and plug your receiver assembly into the cigar plug in the dashboard. If all is well, a second or two after you put the car into reverse, the LCD will light up and show you what's behind your car.
Assuming all is OK, go back and thread all the wires in the trunk lid nicely, and use cable-ties to keep everything neat and in place. In particular, position the transmitter so that when the trunk is closed, the little antenna has good line-of-sight to the receiver in the front of the car. Conveniently, there are two small holes in just the right place to make this easy.
Oh, and don't forget to plug that connector back into the lamp assembly before you put the put the trunk cover back on! And to test it to make sure you haven't messed up the lights.
Then all that remains is to tidy up the cables in the front of the car. For now, I'm just tucking them behind the LCD screen, which just fits in the little compartment in front of the gearshift, but next year I plan to get a 3D printer and may fool around with making a custom mount.
The only thing that isn't quite perfect about this setup is that the camera seems to be tilted a few degrees off the horizontal. I may be able to fix that by fiddling with it a bit, but for now it's perfectly acceptable.
Hope this little tutorial helps a few people out!