Router Limits works with any ISP.
If you're on AT&T U-Verse, you probably have a modem/router that AT&T supplied as part of their service. To add Router Limits, you'll need to log into that AT&T modem and disable the wireless signal. You can then plug Router Limits into the back of the modem and use the signal from the Router Limits router for a protected WiFi connection.
This article might help: http://geekbeat.tv/how-to-use-your-own-router-with-att-u-verse/
Tip: Before you change anything about your existing setup, be sure to activate your Router Limits system at RouterLimits.com. During setup, set the WiFi name and password to be the same as that which your U-Verse is broadcasting. When you make the switch and plug in the Router Limits system, all of your devices will automatically connect to the new router!