This is bullshit. There's no "safe headset" for bike riding, just like there's no safe level for drinking.
If you're really feeling the need to nullify the sublimely powerful and enriching experience that is bike riding (on an awesome bike in awesome surroundings) by plastering over it with the same stuff you listen to at your desk or on your commute - then sure, go to town. It's a free country after all. And yeah, you should probably do your homework and research slightly less intrinsically reckless ways of doing so.
But please - don't call it "safe". That's just bullshit.
Edit: Yes, I can imagine contexts when having an earpiece can be helpful (you can have an agent telling you about upcoming hazards, or of important incoming calls). And for very long rides (on bleak terrain) a bit of music might relax you and make the trip safer. But I suspect many people will use the headsets just to feed their addiction to stimulii, stimulii, stimulii. And in any case, it's still not intrinsically "safe" technology unless used very sparingly.
