Learning JS stuff:

• Bootstrap for UI/widget/look.
• Embed JS for "application" framework (what does it bring? How's that MVC and testing really useful?)
• Kinetic for HTML5 canvas.

Ideas:

• Block editor. Saves locally on server.
• Dashboard showing server data / state. Think piscine enregistreur.
• [...]

Speaking of piscine enregistreur, I don't think I can support velleman's USB stuff on an RPi (never got motivated to find how to deal with the driver), so look into other venues to have voltage measurement.