Whoah dude, that physics demo is really cool. I've been hoping someone would make a flash game with a similiar 'grappling' aspect ever since I played Spider-Man 2 on the original PS2. I never thought about the complexities of the pendulum physics before though.
It sort of sounds like your finished product will be something along the lines of the original Bionic Commando.
<a href="http://en.wikipedia.org/wiki/Bionic_Commando">http://en.wikipedia.org/wiki/Bionic_C ommando</a> if you're not familiar with it.
Really looking forward to see what you guys come out with man, PM me once it comes out, and I'll definitely check it out. (And most likely vote 5)
Egoraptor
Wow, this is pretty awesome!
I've wanted to create a game involving a grappling hook for a really long time, too. This engine is really impressive, smooth, and intuitive. I was web slinging in no time. I hope you make a great game!