18 months ago ESRI acquired Portland-based startup Geoloqi and now has put the startup’s technology to use by releasing a new geotrigger service. The geotrigger service, which was in beta since November, allows developers to more easily serve content to users based on their location, for example, if a user enters an area, send a notification email.
Of course this new service is not free, however you can try it out for with an introductory developer account. Find out more here. The service does use “a fraction of an ArcGIS Online credit” which is 1 credit/12 geotrigger events.