Envoy - Visitor registration that's changing how guests are greeted in companies around the world.
Google Contacts - Google Contacts is Google's contact management tool that is available in its free email service Gmail, as a standalone service, and as a part of Google's business-oriented suite of web apps Google Apps.
Proxyclick - Connect with Confidence
FullContact Card Reader - Automagically scan biz cards into LinkedIn/Gmail contacts
TractionGuest - Safe, secure workplace for all.
Nextcloud Contacts - The Nextcloud contacts app is a user interface for Nextcloud's CardDAV server.