According to this, Lydia Guzman of the group Respect Respeto is texting to a phone tree news about immigration sweeps that Sheriff Joe Arpaio is conducting in Maricopa County, Arizona. The texts are then broadcast to others in the tree:
Guzman said she sends the messages to a wide range of groups, including the American Civil Liberties Union of Arizona, Copwatch and various immigrant-rights...
... for Respect, they're headed by Lydia Guzman who's also VP of Somos America. Per the 2005 page votingrightsact.org/hearings/4705hearing/panelists.html:
Lydia Guzman serves as Outreach Director for the Clean Elections Institute, Inc. in Phoenix, Arizona. Ms. Guzman has more than 15 years experience with voter registration, education and Get Out The Vote campaigns. She was Arizona State Director...