The Satochip Two-Factor Authentication app allows to approve transactions before signing them with a Satochip hardware wallet. The app regularly poll the Electrum server for new transaction proposals. These transaction candidates are then parsed and displayed. If approved, a cryptographic code is sent back to securely and uniquely approve the transaction so that the Satochip can sign it.

Code is available on https://github.com/Toporin/Satochip-2FA