Yes, when the undead are tearing flesh from your neck, you're going to wish you had invested in a piece of wireless communication that is singularly dependent, not network dependent. And the truth is we are still quite network dependent whether by wire or wireless.
Cell phones are wireless, but they depend on cell towers. If the towers where you are ever come down because zombies have scaled them to scout out fresh blood (or bad weather like a tornado has damaged the structure) you're going to be SOL: Smartphone Out of Luck.
Physical damage to cell towers, power outages, and even excessive solar flares can doom your cellphone. According to wnd.com: "Solar flare activity…could be cataclysmic, causing a telecommunication blackout that would down mobile phones and navigational systems."
Traditional Radio Rout
The same goes for traditional AM, FM, or HD radios stations. Bad weather and the undead can both cause physical damage making a radio station unable to broadcast. If the transmitter or tower taken out, there's little a station can do until the repairs are made. I know this from first-hand experience. Most stations have a backup generator but even that can experience malfunction and eventually will run out of fuel unless refilled. The station operators are still dependent on good maintenance luck or operational lines of commerce for gasoline or propane. In other words: there are negative variables.
When I was the Program Director and morning guy at WLOX-AM in Biloxi, Mississippi years ago, a hurricane came ashore and the winds cracked our tower in half. We were forced off-the-air. After the storm passed, the best we were able to do for weeks was jimmy-rig a long cable through our parking lot which allowed us to get a signal out for just a few miles.
Internet Stream Shamble
You can forget Internet Radio if the grid ever comes crashing down. Just take away electricity and your router is gone or the server that provides your broadband is gone. If servers are damaged by weather or natural disaster OR zombies, it could takes days or weeks to replace. Servers hacked? Gone.
Satellite radio might have a chance if the source of content is still viable but a massive power outage in Washington, D.C. or New York City and call in the generators. In an extended cultural meltdown, SIRIUS XM might not have a source for more. Plus: Satellite Radio also depends on ground repeaters to get its signal into certain urban areas dominated by buildings. Grids, grids, grids. You need 'em running or else.