Envoy is a a killer app for Visitor Management. The Envoy app is quick, easy to setup, and can easily be customized for your corporate branding. App fills a small niche, but does it extremely well. Envoy offers an easy to use API for accessing data in the service, and was something we were easily able to integrate with our systems. It's easy to use, and has the features you need for easy visitor sign-in, including badge printing, agreement signing, and host notifications.
The only downside is there is a pretty big jump in price between free and paid tiers, which may limit the apps use in small business. The company does offer discounts for nonprofits and education, so this alleviates that pain somewhat.
Ultimately, the envoy apps leaves nothing to be desired, which is an awesome feeling to have, and yet Envoy still manages to continuously improve it. The customer support and community management teams are awesome, and its rare to find people as enjoyable to work with.