In any emergency, the ability to communicate is critical. With America in a state of "National Emergency", where activists could find themselves eventually as "Enemies of The State" more so that usual, there is a need for activists to make sure their communications are secure. One place to start may be their mobile phones, here are a few apps that I find useful.
Orbot: This is a proxy that filters traffic through the TOR network. It can be configured to only run certain apps through it. Until the TOR project completes a full version of the TOR browser for Android, this is among the better solutions. There is no Orbot for iOs, but thisVPN+TOR pairing seems to be highly rated.
Signal: A lot of us use our phones more to text than we do to talk, these communications hop from one tower to another, and likely a few of them are being watched. The Signal app, available for both Androidand iOs allows for secure communication with other users of the program. It also will allow you to send messages to non-users of Signal, so there's no need for two texting tools.
Cell 411: "Community Defense" is another resource that is necessary in an emergency. This app, available for Android and iOs allows you you send alerts to friends and family in real time. It also includes streaming video capabilities.
Mobile Justice-This app is provided by the ACLU for residents of 18 states to monitor interactions with the police. There is also a separate "Stop and Frisk" app for New York residents.