KDE Connect - Integrate Android with the KDE Desktop
Typeeto - Use Mac’s keyboard to type on iPad, iPhone, Android, etc.
Pushbullet - Pushbullet - Your devices working better together
Type2phone - Type2Phone: Use your Mac as keyboard for iOS devices
mconnect - Vala/C implementation of KDE Connect
Mocha Keyboard - Mocha Keyboard is a leading Bluetooth keyboard application for iPad, iPhone, and iPod touch.