Thanks to the help I've gotten from this forum, especially SingleCell (dev of Caustic) I've been able to update my ReLoop app to have some realtime FX now. For now it has Delay, Low pass Filter, and Foldback Distortion.
The update is out (1.9.0). Each track has its own FX settings. To bring up the FX dialog, just long press on the track number (on the left of the screen) to open its FX adjustment dialog. It's a bit "plain" right now since I haven't applied much polish and sheen to ReLoop yet (gotta find a good graphic artist for it yet).
I've actually found that if you load a bass loop and set the low pass filter down low with mid-resonance, and then turn on Foldback distortion, you easily get 303-style bass sounds
I plan on adding automation as well for the FX and Volume of each track.
Thanks for the help everyone!
-nikotwenty