I had an idea that seems too good for it to but exist, but I'm not aware of it. It would be an awesome addition to Caustic or any music scratchpad type app. What I'm imagining is a way to have a module that triggers a note when audio enters the mic. Even if it did not detect pitch and simply sent an on/off on a single channel based on whether sound is detected would be great for programming rhythm parts. Sometimes I imagine beats that have intricate fast parts that I have trouble describing, but I can record myself drumming them on a surface, then figure out out by figuring out the tempo and working out the notes. I often don't know what I'm doing and end up saying "oh, that's a dotted sixteenth there, no wonder it didn't sound right". It's a very time consuming process, though.
Imagine being able to activate microphone trigger with a check box, while this is on you can't record, but it acts as a virtual MIDI drum pad thats activated by sound instead of pressure. You may lay down your kick with the grid, then set the microphone trigger to the snare, press record/play, and tap a fast snare fill with your fingers next to the mic, and that row of the grid is populated with a nice organic blend of little notes. You would be able to use it on any instruments, you might have trouble getting a fast lead riff to sound right, so you mic-drum it and then move the notes to the right pitches in the pattern editor.
I'd think it would be easy to make it even better, like having velocity vary with volume, or having a separate trigger for each stereo channel, maybe even set different pitches to triggering different channels so you could have a full drum pad with a bit of tuning and finding things that make different sounds when you hit them, but honestly just the simplest version I described first would be crazy useful.