Remote Access To Mobile Devices From WebApp Via HTML/Clientless/WEBRTC Protocols

I currently have a filesharing webapp in development. It is based in CodeIgniter framework. LAMP. When my users "Choose a file" to upload, in the openning windows explorer, I want all their mobile devices to be listed and connected so they can go to the files on each respective device and upload a file from that remote mobile device whether it is smartphone, ipad, laptop or another pc. It doesnt have to be through the file explorer either. Many remote support organizations use html 5 clientless protocols to access files on a user's computer/mobile device ONCE they are granted permission by user, but my users before hand will go to a web page on my site to log their mobile devices in, and stay logged in, so that when they use the site to upload files, the device will appear when choosing a file and files can be accessed on the "logged in" device. IF WEBRTC is involved as well, this is fine.