Claví

Claví restores accents and diacritics directly on your Mac, without going through the cloud. Download only the language pack you need, then type naturally: missing accents are restored in the background, including on text you've already written.
For long passages, use block paste to apply correction in one pass. Accent restoration runs on-device, locally, with a strong privacy model: your typing data stays private.
Made for QWERTY users everywhere: keep your existing keyboard layout, type naturally, and restore accents on the fly without changing layouts.

Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/