detect whether a file has been modified?

[animatorgeek]

I'm working on an autosave panel (being quite dissatisfied with all the others I've tried) but I'm trying to figure out a way to detect whether a document has been modified. The closest I've come is Document.canRevert(), though that only works for files that were loaded from disk (i.e. it doesn't work for new, unnamed, unsaved files). Anyone know a way to detect it for all possible documents?