Among the products and services that AT&T will offer are windows and door sensors (naturally), motion detectors (naturally), connected cameras, door locks, thermostats, moisture and carbon monoxide detectors, and power controls for appliances.
All these controls and sensors use the home's broadband. AT&T will also open company-owned and operated 24/7 security monitoring centers. We'd expect that to also leverage the home's broadband to alert the centers of an issue, but that's unclear. It's also possible the service would use a wired or wireless phone system instead.
Any wired system has its vulnerabilities. Older homes that have wires leading from utility poles can have those cut, meaning that broadband or phone alerts to the 24/7 monitoring center would be disabled.
On the other hand, if the system is "programmed" correctly, that would show up and the monitoring center would / could alert the owner of the home.
The service will be offered nationwide as with its wireless service, and will be part of the AT&T Mobility Group. As is typical with these sorts of things, AT&T will begin with a trial, in Dallas and Atlanta this summer.
The service will be available via AT&T stores or the company's Web site once the service expands nationally. No timeframe was given for that.