I have (had) the J&M XM hook up also and tried to hook up my Ipod by using a Y-Connector I purchased at Radio Shack, however it would not work (even with a ground loop isolator). We tried several different configuarations however there was extremely bad feedback (clicking) with both devices attached. I like J&M products (have the CFRG unit for Radar, cell phone, etc, ARAI helmets, Blue Tooth cell phone unit) but their XM hook-up only provides for one audio source. The J&M XM unit works great for just the XM radio and their customer service has been excellent, it just does not handle two audio inputs.
I ended up buying the Kennedy AuxSwitchSet2 along with the associated cables for the audio and power feeds for my XM radio and replacing the J&M unit with it. The Kennedy unit provides two auxillary inputs that will not interfere with each other. It also provides power to the XM radio and will hook up a radar detector and GPS It provides power for a second audio device, unfortunatly the power connection is not compatible with the IPOD. You have to either run the IPOD on battery or use something like the Electrical Connections power harness described below.
The Kennedy unit sets one device as the primary source and the other as the secondary source. If you are playing the secondary source (Ipod) and turn on your XM (primary) the unit automatically switches the input to the XM. If you are playing the Primary source (XM), turn it off -since it is the "master" and turn on the Ipod. To switch back to the XM, just turn on the XM - you do not have to turn the Ipod off, since it is the secondary source the Kennedy unit does it automatically. The Kennedy unit plugs into the IPOD headphone jack on top.
You may also want to consider Electrical Connection's IPOD wiring Harness to provide power to the IPOD so it stays charged. (The Kennedy units power output is not compatible with the IPOD therfore you only are using it for the audio feed). The EC harness also provides the audio feed out of the IPOD that can be routed to the Kennedy unit by changing the plug in adapters or clipping the adapters and soldering the red, white, and ground (black) wires to each other. Unfortunately the Kennedy unit and EC unit have diiferent size plugs and are not plug and play with each other. It is easy to do - not as bad as it sounds. Note - if you are not running a second audio device such as the XM radio. you only need the EC unit as it has an audio feed. The only problem it is like the J&M unit for the XM radio. It can only handle one audio source. By combining the two you get two audio inputs and a wiring harness that is compatible with the docking port on the IPOD. The Kenndy unit can handle the two audio feeds but not the power and the EC unit can handle the power but not the two audio feeds.
If you use the EC harness to supply power you will also need the ground loop isolator. Attach it between the EC power harness and the Kennedy unit otherwise the Kennedy unit will not function properly. If you don't use the filter, the Kennedy unit picks up intereference which it interprets as an audio signal and does not switch back and forth as it should and it also causes a weak or distored signal in the left stereo channel.
One other advantage of this set up is that it does not use the top headphone jack on the Ipod. The audio feed comes out the docking plug on the bottom (thru the EC harness) and it sounds better. If you do not buy the EC harness, the Kennedy unit plugs into the headphone jack on top of the Ipod. The bottom docking port is not used.
The best of both worlds would be if EC sold Kennedy the harness and have Kennedy incorporate it into their switch (hint. hint) so it would be plug and play.
