I actually made one for myself, there, I fixed it style to be able to mount the N900 on my telescope and to do time lapse photos (also helps with shaky-hand macro). I would post images of it, but... it's kinda embarrassingly shoestring

EDIT: for anyone trying, I'd suggest getting a CP408 case, and then adding a mount adapter to it - sadly, no such fancy cases available here so I had to... manage

As earlier posted Nokia has the source to process the images with high quality output but 30 seconds of high CPU load.

In my opinion it would be a great feature to store the images by default as RAW, convert the Images to JPG using the fast algorithm and when the user press sometimes later (perhaps at home) a button "process now" a batch converter starts to convert all new RAW images to high quality processed JPG's.