FullHunt is the attack surface database of the entire Internet. FullHunt enables companies to discover all of their attack surfaces, monitor them for exposure, and continuously scan them for the latest security vulnerabilities. All, in a single platform, and more. Seems to share functionality with SHODAN in this regard.
REST API: https://api-docs.fullhunt.io/
Free tier: API access, 1K searches per month, 30 results, basic search filters.