Yes, there is Linchpin Mobile.
It is fully compatible with the latest versions of Atlassian Confluence Server and even has a secure Gateway service called Firescope, that connects instances behind a firewall seamlessly without a need for a VPN connection.
Normally you have the problem, that most Enterprise Confluence Server instances are hosted behind a firewall. You either have to connect via a VPN which is very cumbersome in mobile smartphones. Especially non tech-savvy users do not understand the VPN concept and find it annoying to always start a VPN connection.
Using a mobile device management software (MDM like AirWatch, MobileIron, Intune, ...) is a nice workaround, but often involves heavy licensing fees, that kill your intranet use case, where you “only want to inform” some employees without notebooks or desktop computers like cashiers, bus drivers, flight attendants, nurses, …
We solve this with a Gateway service and a QR code that enables end-to-end-encryption between Confluence and the mobile app.
This way a fast, seamless connection between the public app on an employees smartphone and the Confluence server is possible. See this demo video on how it works: