Google Titan - A 2FA device to protect yourself from hackers
Antideo - Email, IP address and phone number validation API service
Instant 2FA - Add two-factor auth to any site in minutes
Alloy - API service and dashboard for identity verification
Two Factor Auth (2FA) - List of websites and whether or not they support 2FA
Verifier - Weed out disposable, non-existent domains or invalid emails.