Hi Rob,
Yes, PTLens is software and it costs. I think its a front end for the Pano tools plugins. The PTLens gives you 10 uses for free as a trial. There are a range of cameras and lenses that it does correction for (but that might be just for geometry - haven't really looked into it). There is a list at the developer's website
More info here and link:
http://wiki.panotools.org/PTLens