COLDCARD uses two Secure Elements, from different vendors, to protect your Bitcoin. Specifically, the COLDCARD uses Microchip's ATECC608 and Maxim's DS28C36B to store the critical master secret: the 24-word seed phrase for your BIP39 wallet.

All of the Coldcard code is viewable, editable, and verifiable. You can compile it yourself.

Only signing device (hardware wallet) with option to avoid ever being connected to a computer, for its full life cycle: from seed generation, to transaction signing. Uses PSBT (BIP174) natively!