I have done this but its fiddly.
Do you have a reverse camera, if yes then don't bother reading anymore
To get video in you have to connect a wire to the back of the DVD unit in the glove box (this is the assuming you don't already have a reverse camera). Now this wire is not available from Honda on its own it comes with the reversing camera so you have to make one. The one I made is pictured below (there are instructions on here somewhere on how to make the cable) you then feed this wire to the central armrest.
For audio in I used a DICE electronics box which has a dock connector and also a 3.5mm audio in jack. This box connects to the back of head unit where you would connect up a CD changer. Then you split the 3.5mm audio connector to a composite Left and Right. The DICE box is shown below with all the cables. Once all connected I routed the dock connector and the composite L & R connector to the central armrest.
So now in the arm rest you have a composite video connector, a composite Left/Right audio in cable and the dock connector. The dock connector is fine just for audio from the iPod but will not send video to the screen as the other end is connected to the CD changer in using the supplied spliiter cable as it will already be in use for the SatNav.
You then need a Apple Composite AV Cable
You connect this to the iPod and then plug in the video out to the video cable you fitted and the audio L/R out to audio L/R you fitted. Below is a rough diagram of th connections.
Now when you play a video on your iPod it displays on screen but only when the car is in reverse gear as remember you are using the reverse camera input for video in. There is a way to add a switch detailed on this forum how to get around this problem.