Although the scales are a little more firmly set in stone that you might like, the Topaz Labs Detail plugin (usable as a quasi-standalone with the free Fusion Express host; otherwise will work with any 8BF-compatible editor like Photoshop, Paint Shop Photo Pro, IrfanView, etc.) works at three levels of detail independently (or as close to independently as possible).

I use it both for capture sharpening/definition (where large-mass and medium detail definition are more important) and for output sharpening (microcontrast levels at and around the pixel level). There is a fully-functioning (no restrictions, no watermarks) 30-day free trial available for download, so you can test-drive it and see if it works for you.

It may not quite have the parametric control you were looking for, but I haven't found myself wishing there was an intermediate level between the ones provided (yet — one should always remember the yet). There is only one major downside to the software (and I'd suppose the same would be true for any software of this type), and that's that it can be very slow with very large images on a poorly-provisioned computer. For instance, a Nikon D800 image on a 1.8GHz Core 2 Duo processor with 2GB of RAM takes well over a minute to pre-process for the detail size divisions (I won't be processing D800 or medium format images on that laptop again), but with smaller images (more typical current DSLR sizes) or on a machine with more memory and processor speed, it's an acceptable performer.