The WiModem232 plugs directly into your Amiga's serial port and gives you the ability to run a BBS using it because all of the standard RS-232 lines are supported (Rx/Tx/RTS/CTS/DTR/DSR/DCD/RI).
I've been wanting to get my BBS back online for years. But what's the advantage of using this over telnet? I suppose one might be it's a lot easier to set up as the BBS program receives it's data through the serial port device as expected. Perhaps another is this doesn't take up any ethernet network bandwidth?