no looping on the Android version (v1.0.4) yet.
Guitar playback... do you mean like AmpLink, iRig, Amplitube etc? I am not aware of anything at the moment. Other Android members might post.
Before we supported background audio in iOS, there were some posts on using units such as Korg Pandora etc. Search for those.
Also here is a starting point: http://www.korg.com/pandoramini