DIY Bitcoin signing device built from off-the-shelf Raspberry Pi Zero parts (~$50-70). Stateless: powers off with no private key storage. Air-gapped QR code signing. The most sovereign hardware option — no trust in any manufacturer.
SeedSigner scores 87/99 and Sparrow Wallet scores 87/99. Use this page as a starting point, then review each provider profile for ownership, warnings, and policy changes.