There are some apps that will support the TWA. Unfortunately on Android, they are kind of limited with the features and will not work with the iDevice. iRig is a good example, but you will not be able to feed the effects back to the TWA.. SampleTank is by far the best app available for use with the TWA. I'm hoping IK Multimedia will put out something similar for Android in the future.
If you ever come across an app that you think may work please please PLEASE let us know!