The Everykey device holds a decryption key (or key-equivalent) for your keychains, and it has over-the-air upgradeable firmware? Even if the firmware is signed, and the upgrade procedure is password-protected, the feature may expose the device to a variety of different attacks.

(Not to mention hardware attacks, since even if the device has a secure element, it has to send key material back to the device with the keychain.)