While there are fascinating projects out there for DIY hardware wallets, it's extremely important to remember the purpose of a hardware wallet -- securing your private keys against common attacks, even if the attacker has the physical device (but not the seed/backup/passcode).

If you use a standard device like an old Nokia, anyone with access to it could easily scrape keys off the device. Utilizing a secure element and hardware designed to be as secure as possible (like in the Passport) makes it extremely difficult for an attacker to get your private keys without having the seed/backup/code in hand as well.

We do realize that the price of Passport can be out of reach for some, and that's one of the reasons we're working on expanding Envoy's feature set -- even without a Passport.