Boomerang is a service that works with your Gmail to send e-mail later, give you follow-up reminders, and notify you if you don't hear back within a specific time. To use the service in the past, you had to install an extension for Chrome or Firefox.
One big reason for using the app alongside the desktop version is that you don't have to wait until you're at your desk to schedule an e-mail or a reminder about an e-mail.
Ready to test it out? You'll need to install a copy of Boomerang: Email App for Gmail on your Android device.
When you open the app, you'll be greeted with the option to sign in using a Google account. After signing in, a slideshow tutorial will load highlighting the features of the Boomerang app.
To start using the features specific to Boomerang, you'll need to either write a message or select one you want to work with. If you're writing a message, you can decide when to send it by pressing the Send Later button at the top of the app.
You can use the Boomerang option to alert you if no response is received within a specific amount of time. The Boomerang option can also be used for new messages, if you don't feel like dealing with them right now, but want to receive a reminder about them later.
The Settings menu for the app is particularly small, only letting you adjust actions for left and right swiping. Actions to choose from include archive, delete, and other message actions like the Boomerang option itself.
You may notice that two new labels are created in your Gmail account, one for Boomerang and one for Boomerang-Outbox, both of which are used to track your messages with the service. Also, the style of the inbox is very different-looking from the stock Gmail app. Sender names, subject lines, and excerpts from messages are displayed in what Google would call "comfortable" space. This will either make the mail list easier to read or annoy you with wasted space.
Keep in mind that this app is brand new, so there's going to be a few kinks that need to be worked out. If you have an issue, Boomerang responds to user feedback very often, as seen by the app entry on Google Play.
Even though the current app only supports Gmail, Boomerang has stated that it will support services such as Outlook, Yahoo, and others in the future.