Demo (in sunny weather) of the OSD functionality on the extension board:
And in very bad weather:
The Extension Board has an optional OSD-ic soldered to it. Make sure to order it with the OSD option.
The gluonpilot can directly interface with the MAX7456 On Screen Display chip. It connects to the Gluonpilot's SPI port (which is available next to the FTDI connector). It should be supplied with 5V, so don't forget to set solder jumper SJ1 accordingly.
For people interested in modifying the OSD-code, this website can be of a lot of help.
Where to get this OSD-chip: