Ask HN: Like Hemingway app, but for writing sales copy?

Hemingway [1] is fantastic at tightening up my normal writing, but for landing pages, sales letters and promotional emails it's not that helpful. With the quantity of effective sales copy out there, it'd be great if software could help write higher-performing copy than I can on my own (not difficult). I've not found any prior art - have you? If not, consider this a free software idea... [ I have contacted the authors of HemingwayApp, but no response to date ] 1. http://www.hemingwayapp.com/