Hi Dan, thanks for sharing.
Regarding your question
if it would be possible to add a field to OpenSprinkler’s Preferences page to switch between default behavior (using rayshobby server) and another URL (e.g. the server on the raspi)?
this can be done by adding an string option that stores the prefix to the Javascript path.
If you have a write-up, I would be happy to post it on my blog. Is it possible to share just the changes/files you made, instead of the entire linux image file? I assume a user would want to install the default Raspi image first, and then follow the change you made.