Synergy - Cross-platform software for sharing your mouse and keyboard between multiple computers
Type2phone - Type2Phone: Use your Mac as keyboard for iOS devices
Input Director - Control multiple windows systems with one keyboard/mouse. Share a keyboard and mouse across multiple windows system.
Typeeto - Use Mac’s keyboard to type on iPad, iPhone, Android, etc.
Ultramon - UltraMon is a piece of software built to help with the management of multiple screens on the same computer system. Without software like this, taking full advantage of an expanded desktop space can be difficult.
Unshaky - Dismiss duplicate key hits on MacBook butterfly keyboards