I am using a L5 Remote Dongle to turn my iPhone into a universal remote (see http://www.l5remote.com/). It is working fine with my Bang&Olufsen equipment.
Unfortunately the L5 can not learn Beolink 4 commands by itself, but you can programm the L5 with pronto hex codes. I found some pronto hex codes of Beolink 4 commands at http://www.remotecentral.com/cgi-bin/codes/bang_&_olufsen/beosound_9000-st-cp/, but many link key commands are missing.
The following commands I could not find there and would be very usefull for me:
1) PC (to choose the source PC)
2) DVD2 (to choose the source DVD 2 via my Beosystem 3)
3) Stand (to turn the stand of my TV)
4) Link Radio (to choose the source main Radio within a link room)
5) AV (to listen to radio in main room, while TV is showing the picture)
6) P-IN-P (to get a picture in picture)
7) Format (to change the format at my TV)
It would be great, if somebody could provide the relevant pronto hex codes.