Currently SolarUser supports node data alerts based on posting time, e.g. "not posted in a while". It would also be useful to support data threshold based alerts, e.g. "source X falls below Y for more than Z minutes". The alert should support time-based constrains like the existing data post alerts, e.g. "only trigger this alert between 9AM and 4PM".

It would be quite useful to support various comparisons, including less than, equal, more than, and matches (regex).