Digionica SyncTool - Digionica SyncTool is a useful utility that has been designed for synchronizing files and folders in numerous computers on the net, on local storage, and on servers.
Pushbullet - Pushbullet - Your devices working better together
arRsync - arRsync is a tool that is designed for macOS that is used for transferring and synchronizing files between a computer and a storage drive.
Plover - Browser Airdrop - transfer files to anyone, any device
MirrorFolder - MirrorFolder is a real-time folder synchronization and backup software
blymp.io - Transfer files between any device with 4-digit codes