I have been working on Apple 1 peripheral board designs for the past several months and have them nearly completed. The boards all can take advantage of a simple Apple 1 mod which allows the VMA line to become useful. With this line active, peripheral boards can disable all on-board addressing so that peripheral boards can act as a substitute. The boards include an RS232 Serial board, a USB interface that can make the Apple 1 output appear as a keyboard to a PC or MAC, and a non-volatile memory board that can appear in any Apple 1 address space. There is also a buffered expansion board to support multiple peripheral cards.
I have put descriptions and demo video links on my web site http://www.apple1notes.com/old_apple/Peripheral_Boards.html
(edit by eeun: fixed period at end of link)