Does exactly what it says it will: detects faces and blurs them automatically. It’s also easy to manually add, adjust, or remove blurs as you see fit.
I removed one star because it lacks the ability to process more than one photo at a time. I’d like to be able to load a batch of photos in, flip through them all to check the results, and then save them all at once. Right now you have to do it one at a time, and it’s quite tedious if you’ve got a large number to do.