There's a danger to this though; if drone pilots are universally expected to be warned when they fly in dangerous areas, then pilots will start flying "to the edge" and expect the technology to always keep them in line. I would be surprised if restricted areas were stable enough that drones could store a database of no-go areas and keep it up to date easily.

It would be more straightforward to set clear policy and provide a way for drone pilots to know where not to fly (e.g., provide an online map and require altitude telemetry to the controller at all times). Include a link to this information with every drone purchase.

My guess of what will happen if we go down the GPS route: Some incident with a drone will occur, and the pilot will say something like "the drone didn't warn me that I was in a restricted area".