Simple Keyboard is described as 'Features: * Small size (<1MB) * Adjustable keyboard height for more screen space * Number row * Navigation keys * Custom theme colors * Minimal permissions (only Vibrate) * Ads-free Feature it doesn't have and probably will never have: * Emojis * GIFs * Spell' and is an app in the OS & Utilities category. There are more than 25 alternatives to Simple Keyboard for a variety of platforms, including Android, Android Tablet, iPad, iPhone and Windows. The best alternative is AnySoftKeyboard, which is both free and Open Source. Other great apps like Simple Keyboard are Gboard (Free), Microsoft SwiftKey (Free), OpenBoard - Keyboard (Free, Open Source) and Hacker's Keyboard (Free, Open Source).
Any Soft Keyboard is an on screen keyboard with multiple languages support. This is one of the most customizable keyboard available. To activate: Launch 'AnySoftKeyboard Settings' App, and follow the instructions.