Using Magus is simple. The whole system is based on six simple gestures -
Get it? No? Watch the video.
These gesture combos work even in screen-off mode, therefore it offers a literally true stealth mode -
recording voice or taking picture without even unlocking the device! Isn't that great? Imagine the possibilities!
However, the app is currently in beta-stage and if you want to try it out, you have to ask the author for permission. Don't be sad, you'll surely get the answer within few hours (like me).