Short Idea Memo
Short Idea Memo is a memo widget application that uses Markdown notation, which expresses text decoration with symbols. It allows you to write down ideas that come to you in your daily life in an easy-to-understand manner.

Based on CommonMark, it applies its own extended rules for color expressions, underlining, and other expressions. You can also create checklists and tables, which are useful for noting down your plans for shopping, task lists, etc.The background and text color of the widget can also be changed from the settings.
Any text that doesn't fit in the widget can be scrolled to see the rest.
The text editor has a toolbar from which you can apply markdown formatting to the selected text. It also supports multi-step undo and redo, so you can easily deal with mistyping.
If you are not familiar with Markdown, you can apply formatting from the toolbar.
The edited text can be saved as an HTML file, which can be viewed in almost any browser application.

It supports online storage services OneDrive, DropBox, and Box and as long as you have an account with each, you can back up your notes with a single touch. Of course, you can also download them, so it's easy to share your memos on multiple devices.

The peek-proof function automatically hides the contents of the widget when the device is locked. This is a simple system that reappears when you touch the widget, but it prevents your notes from being easily seen by others.
*I can’t fully guarantee for peek-proof, because the power saving feature of smartphones may force this feature to stop.

Get it on Google Play