I always thought that it will be really nice to play, slow down, loop, change keys directly from iPod. Last week, it dawned on me that there might be a iPod app out there that can do this. With some researching, I finally found one! It is iLift app. It does exactly what I was looking for and it is free!. (Free version only lets you add 3 songs in its playlist, but it is enough for me for now) I hook this up with my POD Live x3 playing "Savior of the World" by Ben Cantelon from key of B to G and it worked really well. I was able to loop the intro so that I could repeat it again and again.  

It is really difficult to practice with songs with keys that we don't really sing with. iLift will help you to do this much easier. Try it out and let me know how it you like it. Enjoy!

Here is YouTube demo video.