Email alerts are available for signed-in users who subscribe to a public alert for a station (the in-app subscribe flow). Stations can also attach public or private alerts and calendars to measured datums (channel bottom, bridge clearance, and the usual tidal zeros). Sentient Things owners have that today; NOAA, SECOORA, NERACOOS, and USGS stations are getting the same capability. See datums.
Do not expect a lock-screen banner or text message from Tide Alerts in this release. If you need a reminder on your phone, use calendar subscribe for high/low (and related) times.
There are no in-app purchases tied to alerts.