OpenDrop: An Open Source AirDrop Implementation
It is 2019, and it is quite surprising - and disappointing - that we STILL haven't universally solved the means to easily, securely, and (yes, I'll use this term again) universally share files.  I wish we could share files in a peer-to-peer fashion securely without hindrance of mobile platform, nor blockage of network MiTM, etc.  </sigh>