Cool idea, but it should be at least as good as the regular camera app once youre filming something, and right now its still a little clunky.
For pre-recording to occur, the app needs to be open, and in the foreground, and pointing at something. Not always practical with a phone, you generally dont take your phone out of your pocket until you want to use it.
But would be useful in situations where you anticipate filming, but just want to film here and there, maybe at your kids soccer game or something, and youre prepared to sit with the app open and your lens poised, but dont want to fill up your phones memory.
Cjv12 about Precorder: Video Camera for Unforgettable Moments, v1.3