I have an 03 Harley E-Glide. No wise ass remarks about this big ol piece of American Iron please, it's like a big ole comfy couch. It has a stereo system that includes an auxillary jack to plug is stuff, like MP3 players and satellite radio. I have a small XM radio hooked up and into the aux port. I almost always use this radio cause I always get reception. In comes my problem. I recently received a HD (Garmin) GPS. It has voice prompts, and to hear these it also has to be plugged into the aux port. I need some sort of device that I can plug both into, and then into the Aux port. It would ideally give priority to the GPS when it is giving prompts, and switch back to the radio when the GPS is silent. Any suggestions, ideas, advice??

A circuit that gives priority to one channel will probably require a DC power source of its own (small built-in battery, or wired into the bike's 12 volt battery), which complicates things.

However, if you're willing to live without priority, a simple headphone adapter that allows 2 sets of headphones to be plugged into one iPod should suffice. Just about any place that sells MP3 players should carry them.

Quoted: I have an 03 Harley E-Glide. No wise ass remarks about this big ol piece of American Iron please, it's like a big ole comfy couch. It has a stereo system that includes an auxillary jack to plug is stuff, like MP3 players and satellite radio. I have a small XM radio hooked up and into the aux port. I almost always use this radio cause I always get reception. In comes my problem. I recently received a HD (Garmin) GPS. It has voice prompts, and to hear these it also has to be plugged into the aux port. I need some sort of device that I can plug both into, and then into the Aux port. It would ideally give priority to the GPS when it is giving prompts, and switch back to the radio when the GPS is silent. Any suggestions, ideas, advice??

if it is a small (2.5mm plug) or any size for that matter , I think there is a switch box for this purpose.
If not just get a splitter and run em both to it. You may hear them both, just make the volume on the GPS LOUD