A simple app with a simple purpose, Rethink is a strong organization app that’s great for setting reminders and to-dos in an elegant way. Users type in their task of choice and then set a notification trigger: On the free app, that can be time or a location, to remind you to pick up milk when you pass the store. The paid version of the app, for $1.99, will also remind you when a certain person calls or texts, or even when you connect to a familiar WiFi network — so that you can remember to download those files at work, for example. The app itself is great, though users should note that the location sensor can drain your battery if you don’t set the app to check where you are less frequently. You can choose multiple triggers to set off reminders, and the app also makes it easy reorganize your tasks as needed. Free for Android devices, paid version costs $1.99 for additional features.