The Boston Globe reports on two such apps: Secureafone and Word Bully.
Secureaphone, which works on iPhone and Android devices, allows parents to set a geographical boundary for their children to use while trick-or-treating, and it sends out an alert if the child strays beyond that boundary. The app also has GPS tracking software to alert parents if teens are driving too fast.
Word Bully, which works on Androids but will reportedly be available for iPhones before Christmas, blocks incoming text messages that contain any of 3,600 "mean words" that the app attributes to bullying behavior. The offending messages are sent to parents' phones, along with the sender's phone number.