* Auto-Birthday - if you have a contact in your android contacts that has both a mobile number and a birthday in their contact info, you can choose to send them an automatic "Happy Birthday" message on their birthday at a specific time. Can do it with hundreds of contacts. Doesn't use hardly any battery or resources.
* Wrecker - stupid simple "throw a ball at a tower of bricks and try to clear the board" game. High score tables. Made in unity. High battery when in use, No battery use when not playing. Will use internet for high score data.
* GeoNote - Create Geo-fences to generate a notification when you enter a location with your custom text in the notification. My wife is always telling me, "Next time we're here, remind me to only order one piece of toast" or something like that, so I make a note, it pops up the next time we're there and we're both happy. Notes are stored locally. No internet access required. Uses Geo-Fencing which is more battery-friendly than always-on GPS access.
All my apps are free, very privacy-focused and as battery-friendly as possible.
No information leaves your device (other than the high score data in Wrecker).
You have to side-load my apps though. I'm not putting them on the Google Play Store. They're so annoying to deal with! OMG