I want something to generate searchable documentation like this:
http://docs.torquepowered.com/torque-3d/official/

I think if Invision had something like this already, I would know about it, but I thought I'd throw it out there. Any suggestions for alternatives that will work well together with ip.content?

We have a documentation generator for modification authors here: http://community.invisionpower.com/index.php?app=core&module=resources

It's not going to generate the same kind of documentation, but it might be a start for you.

that looks a lot like the documentation doxygen generates include the search. It's not done by doxgen but very similar all the same.