It's basically a super remote control scripter (Logitech Harmony eat your heart out!).

Here are the features I'd like to implement:

Plays DVD*, Bluray, & Common Audio/Video file formats.
Skip selected frames of video/audio*
Mute audio for selected frames of video*
Place still images over selected frames of video (support transparency)
Add sound files to audio
Place text into video (custom subtitles, credits, or old timey "action cards")
Play video file (deleted or alternate scene) from HDD during DVD/BD play
Go to any part of the video (skip long scenes, jump backwards in timeline, insert deleted/alternate scenes on the disc)
Control external devices**
Fade selected frames (to black, or other colors)
Fade audio (to silence or other colors)
Pause video while audio plays

Probably more that I'm not currently thinking of.

*Supported by the MovieMask software I already have

**I have some accessories (lights, smoke, etc.) that I can control via USB that I would like to tinker with movie synching. Like Matinee, only USB'er. The software would handle audio (mp3, etc.) files as well, so I can use it to record and playback custom light shows for individual songs. Or you can use it to turn your USB toaster off/on during a movie too. Whatever floats your boat.