BiModem
BiModem was one of the last file transfer protocols developed for use in BBS systems. It was created by Erik Labs, and was revolutionary for its day.
Unlike the predominant protocols of the day (XModem, YModem, ZModem), this was a bi-directional protocol. In other words, you could upload and download files at the same time. In addition, it had a chat feature. This would allow the user and the Sysop to converse during the upload/download of files.
It never recieved wide-spread acceptance however. It had to be manually patched into both BBS and Terminal software packages, and it was incompatible with some programs. It was released in the end of 1989, and before it saw wide spread use, the Internet revolution came along and made the BBS system obsolete.
The final version (BiModem 1.25) was released in 1991, and all development was stopped after that.
In 1995 a program was released in Argentina called BiModem Pro 4.0. This was a user modified version of BiModem 1.25 with some minor bugfixes.