Envoy - Visitor registration that's changing how guests are greeted in companies around the world.

Todoist - Todoist is a to-do list that helps you get organized, at work and in life.

TractionGuest - Safe, secure workplace for all.

Remember The Milk - Remember The Milk is a task and time management application for mobile devices.

The Receptionist - The Receptionost is a visitor managemnt solution that has visitor logging system to track visitor traffic.

Org mode - Org: an Emacs Mode for Notes, Planning, and Authoring