I just received my Soundgate AUX3 from Logjam electronics. This device allows you to have 3 auxiliary sources into you HU with a dash mounted selector switch (that is a little smaller than a nickel) I have benched tested it and it does exactly what I wanted. I can now switch from the Factory Dash AUX, iPod input and my XM seamlessly !
Physical install is this weekend. It utilizes a "Main Output" (to HU AUX connection converted to RCA) "Main" RCA input (Dash Aux Jack converted to RCA), "Source 1" (iPod via 3.5mm stereo to RCA cable) and "Source 2" (XM Roady vai 3.5mm stereo to RCA cable)
Oh yeah, I am also installing the PIE Line Driver between the "Main Output" and the "HU AUX input" to boost the signal sourrce of all the inputs.
Woooo Hooooo.... I've been looking for this solution for a while.
Linky to AUX3:
http://store.yahoo.com/logjam/soundaux3.html