JP Customs also has a PAC adapter that allows your steering wheel controls to double-up and control an aftermarket DVD player. It's a bit foggy to me as to the vehicle MY compatability. I couldn't find the link when I returned to the JP Custom's site but it appears the item's been out for a while.
Here's what I gathered at PAC's site:
The SWI-V converts the steering wheel radio buttons to 'DUAL' multipurpose controls. The SWI-V allows control of an aftermarket Audio/Video system using the vehicle?s factory steering wheel radio controls, while maintaining normal control and operation of the factory stereo. The interface will control most audio and video products that have an IR remote control. A remote IR emitter attaches to the front of the Audio/Video IR window. The SWI-V solves the problem of lost remotes in a vehicle and it allows the driver to control the video system without taking his/her hands off the wheel or eyes off the road.
Note: The SWI-V interfaces will only work with infrared remotes that use a 38-40kHz carrier frequency. Consult with equipment manufacture to determine the carrier frequency.
Currently these radios from will not work: Sony XAV-7W, CDX-MP80, CDX-MP70, CDX-M850MP, CDX-M3DI, CDX-M800, CDX-CA900X, MEX-5D1, MEX-1HD, CDX-M730, CDX-M770, CDX-M620, CDX-M670, CDX-CA850X and CDX-CA860X units. Delphi XM SKYFI. Denon head units are unknown at this time.
Appl Guide (PDF)