FocusList and Forest both help with planning and productivity by helping you organize your day into blocks of time and helping you stay on that schedule. Other good organizers include My Study Life and Google Keep.
iA Writer for Mac iOS and FocusWriter and WriteMonkey (for Windows) are geared especially for writers. They provide clear formatting and even features such as highlighting one line of text at a time to help with attention to details.
If you like to simulate a particular atmosphere for writing, you might try Coffitivity, which simulates the sounds (though not the smells) of a coffee shop or Paris Cafe or Brazil Bistro or Ommwriter, which provides an array of soothing backgrounds and sounds to help your writing-self feel at ease.
Finally, if you want to track how much time you are actually spending on any device, Hours may be just the app for you.