With reference to a question Harald asked yesterday: There is a way to automatically scale value ranges without having to manually convert them. It’s not a dedicated external, but an abstraction by Hans-Christoph Steiner, one of the gurus in the Pd scene.
All it needs is the desired range of numbers as two arguments (lower and upper range limits). Manually converting might still save you some CPU cycles, though 😉
Also, Hans-Christoph did a lot of work on the HID-object. If you are interested in using controllers with Pd, be sure to check out his HID&mapping objects.