Use this thing if you want to be able to call get and set methods on an object but always be sure to run the value through a function first.
Imagine you have a SPAN element. You want that element to be money formatted number. You can wrap your variable in a SubtleTransformer.Currency and then every time you do myElement.set('value', 1234.5) it'll run the number through a function that'll format it as currency. Then any time you call myElement.get('value') it'll run the value through another function that'll convert it back to a float!
Imagine the aswome!