I have recently switched to Ring Alarm from SimliSafe. Ever since i switched, I missed the ST integration, and I decided to create one.
I have created a custom device and app for integrating ST with Ring Alarm. The integration is using a bridge application as Ring Alarm uses WebSockets for communication and ST does not support that. You can check the integration here https://github.com/asishrs/smartthings-ringalarm.
Deploying the bridge Lambda in AWS might incur some charges, per my calculation it is less than $1.