OneTapMail

If you are exhausted to write daily-boring mails, let's save your time by this app.
Set up message, add widget on Home screen or Lock screen, and tap the button. Your message will be sent without annoying operations!
(To add widget on Lock screen, Android4.2 or up is required)

You can save up to 4 buttons with different settings, and for each buttons, you can choose SMS or Gmail for method to send.
In order to send Gmail in background, you need to authenticate this app.

Any feedbacks with device name and OS version are welcomed!