The action bar is found in the quick menu, advanced search, group details pages, person details pages, and device details pages. It looks a little something like this:
From the action bar, you can phone, SMS/direct message, create an alarm for, check-in on, and locate whichever person, device, or group you choose.
Simply select any of the four options, and then choose from the actions provided. In the image above, you can see that I've chosen to message the user, and I'm then given the options to message them via SMS (cell number), email, or direct message.
From left to right on the action bar you have: phone/broadcast voice message, SMS/direct message, create an alarm for/check-in on, and locate.