NFC Ring Unlock apk content rating is Rated for 3+ and can be downloaded and installed on android devices supporting 15 api and above.
"IMPORTANT: This app uses the Device Administrator permission. Using NFC Ring Unlock is not as safe as using a native unlock solution but at least if you need to change your password, you can without having to replace your finger-tips.
Unlock your Phone or Tablet by holding your NFC Ring on your Phones NFC Sweet Spot. NFC Ring Unlock can be used in conjunction with other lock screens.
This is beta software, please help us make the software by reporting bugs as soon as you find them!
For Common Questions, Answers and other reference please see the wiki: https://github.com/mclear/Android_NFC_Ring_Unlock/wiki
Please file any problems/bugs/issues in our bug tracker: https://github.com/mclear/Android_NFC_Ring_Unlock/issues/new
UPDATE: NFC Ring Unlock is now back, it was removed because NFC Unlock was native in Android however it was recently removed so we have decided to re-publish the app."