Chrome extension in python?
Although you mentioned you don't want it to be a hosted app, but this is one typical scenario where a hosted app can do. 
SciPy is not a package that is easy to deploy. Even if you are writing a installed application based on SciPy, it requires some effort to deploy this dependency. A web application can help here where you put most of the hard-to-deploy dependencies on the server side (which is a one-off thing). And the client side can be really light.
I would like to create a google chrome extension. Specifically, I'd like to make a packaged app, but not a hosted app. Am I correct in thinking this limits me to JavaScript (and HTML/CSS)?
My problem is that I need to do some complex math (singular value decomposition, factor analysis) and I don't want to write algorithms for this in javascript. Python already has libraries for the functions I need (SciPy), but I can't find any indication that I can make a Chrome extension using python.
Is this correct? Do I have any other options?