EditPlus provides this feature. It passes the selected text (or the whole buffer if nothing is selected) to stdin and replaces the selected region or entire buffer with whatever is returned to std out. It’s very useful. You can undo the changes because the buffer is modified not the actual file on disk.

On the bright side. You can accomplish the same thing using macros. It works just as well and provides even more control. I can post an example if it is helpful.