It looks like Sprint just became the first cell carrier in the US to turn on "Wireless Emergency Alerts," which basically means that Sprint subscribers can now receive emergency text message alerts from FEMA, the president of the United States, the National Weather Service, and from state and local emergency operations centers based on location. Users have to opt-in, but the process is really simple to get this set up on your HTC EVO 3D.
Just open your phone dialer and press ##2627# (that's ##CMAS#). Then, make sure that CMAS enable is checked. So far, I haven't figured out a way to get this working on the EVO View tablet, as the normal calculator work-around isn't working in this case.
Also, if you live in any of New York's five boroughs and you have this enabled, you might soon experience a test that Sprint is conducting with New York City authorities. For more info, you can read Sprint's full press release at the link below.
Update: This process does not seem to work on the older EVO 4G. Additionally, your miles may vary if you are running anything but a stock ROM on your EVO 3D.[Sprint]