Hi azzoor
First of all welcome. Second of all - sorry I have been busy and chronically behind reading posts... so this is a little late.
The speed input is as has been described - I don't think it ever worked in an impressive fashion (nobody raves about it and I noticed no benefit from the function in my FD), which is why I think it was dropped from some headunits.
In answer to your other questions... I am pretty sure there is another topic or topics covering/discussing them recently by another member looking to do same or similar
- One was how a member fitted an aftermarket camera to an GD-02 or GD-03... I can't say for certain but I seriously suspect, in any event, there would be little or no difference between the GD-02 and GD-03 regarding camera fitting... from memory they only ran the video signal and video ground to the headunit. That member has a slight issue that their after-market camera generates a parking grid and so does the headunit - something to consider if ordering a camera.
- It maybe in the same topic or another... where there was discussion about the separate USB port on the back of the headunit. I think it basically comes down to either a) if the wiring is already present (which it *might* be if there was an option to have the GD-03 fitted) or b) if it isn't - then investigation maybe needed... I don't know if anyone has actually done it yet (or more precisely written about it having done it).
Could be as simple as getting a cable if the usb port in the cabin is wired directly to the headunit for both the GD-01/02 and GD-03 - in that case the thing would be weather the cable is pre-made (such as if the plugs/sockets on the back of cabin usb panel hasn't changed between GD models/headunit combination) or needing to construct one. It maybe more complicated if other electronics is involved.
