In addition to some of the cloud services Matcha supports, I would also like to see support for SMB (Server Messaging Block https://msdn.microsoft.com/en-us/library/windows/desktop/aa365233(v=vs.85).aspx)
SMB allows you to access files on any windows computer after entering the computer's IP address, username, and password. It is also supported by many Network Attached Storage (NAS) devices (external hard drives accessible via your router). Generally, I've seen WEBDAV supported by third party apps, but apps like Documents (readdle.com) and FileBrowser (https://itunes.apple.com/us/app/filebrowser-access-files-on/id364738545?mt=8) do support SMB. The reason why I prefer SMB is because usually, it's supported out of the box without any configuration by the user (making access to files on your computer a lot easier), while WEBDAV needs to be configured by the user.