Yes. Indicator alerts work on built-in indicators and on wrun scripts. Open the alert dialog from the bell on the indicator's legend row, from the chart's right-click menu, or from Alert on, Indicators in the alerts menu. Pick an output or a signal, pick the condition (crossing, entering or leaving a channel, moving up or down), and save.
For your own script, two things matter:
- Publish it first. An alert runs a published version of the script; on a draft, the chart asks you to publish.
- Declare the signals you want. Every drawn output can be a condition, and an
alert()call in your code adds a ready-made signal to the alert dialog. Alerts in the wrun docs shows how.
OpenMarket checks indicator alerts on its servers, at most once a second for each indicator, so a value that crosses a level and comes back within the same second can be missed (when an alert checks and fires). How many you can keep armed at once depends on your plan (Plans and limits). Custom scripts do not run on CME futures yet, so neither do their alerts.