The is an emulation of a Moog synthesiser: three oscillators, noise, mixer, filter and two envelope generators fully emulated in software with modulation from third oscillator and/or Noise/S&H.
The app supports pressure sensitive touch screens, X/Y accelerometer for pitch and mod wheel, multitouch and zooming interface facilities. The original was a monophonic instrument however the emulator can operate as a polyphonic (duophonic) synth via multitouch when it is enabled. The interface has options for fat-finger, analogue filters and rich oscillators however these will consume extra CPU cycles. The interface also has a full piano keyboard setting.
So this is not Moog and it isn't a MiniMoog, but it does fit in your pocket and your budget.
Interface zooming can be done either with the trackball (Nexus/HTC have them) or enable multitouch via the menu then tap the screen with two fingers at the same time - this will zoom the interface in/out. If you tap with two fingers but keep them held you can move the screen around. This kind of helps out with the dense graphics.
Patches are saved on the SD card along with factory sounds, there is an export and import option to exchange patches. The emulator will, per default, attempt to run with a set of options that will give reasonable quality and the lowest possible latency/lag. The quality of the audio can be tuned with the menu options however the lowest possible latency for pretty much all Android devices is currently 42ms, on my HTC Desire it is 70ms. If you understand what this means then the value might seem quite high but the app is still a lot of fun.