I think the first question is - what is your HR system? Are we talking HCM?
An event agent can be used to trigger an event. It really depends on your granularity. Do you have an actual need for a 30 second response time on creating the account? Can you live with 30 minutes? If so, you can just schedule a delta import every 30 minutes and not only will it create new users but all updates will come through.
You can configure it to do anything once you have the data. If there is some data in HR that will tell you what you need to know, you can attach any number of jobs to trigger when its updated.