What are some alternatives?
When comparing CellSend and SHAREit, you can also consider the following products
Pushbullet - Pushbullet - Your devices working better together
Send Anywhere - Send whatever you want, wherever you want
Pushover - Real-time notifications on your Android, iPhone, iPad, and Desktop
FilePizza - Open source application used to transfer file via WebRTC and WebTorrent.
AirMore - AirMore is a cross-platform toolset that can help you manage any Android device wirelessly.
Dukto R6 - Dukto is an easy file transfer tool designed for LAN use.