Bought one and installed, it connects to the high speed port at the bottom of the GC and runs in progressive or interlaced mode.
Here are a few pics of the item with one screen shot, there are various options, e.g. color of the GBA, Full screen or normal screen (make it looks like you are playing on a normal GBA), Controller settings, soft/normal/sharp picture, ...
http://www.felixmcli.org/gbp-1.JPG
http://www.felixmcli.org/gbp-2.JPG
http://www.felixmcli.org/gbp-3.JPG
http://www.felixmcli.org/gbp-4.JPG
http://www.felixmcli.org/gbp-5.JPG
http://www.felixmcli.org/gbp-6.JPG
Here are a few pics of the item with one screen shot, there are various options, e.g. color of the GBA, Full screen or normal screen (make it looks like you are playing on a normal GBA), Controller settings, soft/normal/sharp picture, ...
http://www.felixmcli.org/gbp-1.JPG
http://www.felixmcli.org/gbp-2.JPG
http://www.felixmcli.org/gbp-3.JPG
http://www.felixmcli.org/gbp-4.JPG
http://www.felixmcli.org/gbp-5.JPG
http://www.felixmcli.org/gbp-6.JPG