Has anyone made a wallet that doesn't access the internet so that it is 100% safe?
Yes. That's what an Armory offline wallet is. Nothing is "100% safe", but an Armory offline wallet done correctly is one of the safest options available for keeping your private keys private. It's software that you run on your choice of offline hardware.
Yes, people have built Armory for a Raspberry Pi.
Like Armory Hardware.
No, Armory is not currently offering hardware built by them to house their offline wallet software (AFAIK).
They should think about it.