Let me assume, for a moment, that your question is more about what you can do with an EMT-B cert besides riding an ambulance. Because there are other things you can do with the cert at 911/EMS and transport companies besides ride an ambulance. In the company I work for, the turnout supervisors (those who hand out keys and equipment, who assign and re-assign shifts based on call-outs and unexpected problems, who do performance reviews on the road crews, etc.) are required to be at least -B.
With both private companies I've worked for, dispatchers were also required to be at least -B.
Consider amusement parks. Six Flags hires EMT-Bs for on-site first response to emergencies. Usually they are glorified Band-Aid hander-outers, but I'm sure they see some action now and again. Similarly, consider any type of fixed facility that attracts large crowds and is opened daily; for example, zoos. I throw in the "opened daily" part because (in my experience, although your area may be differenet) stadiums and arenas usually hire a private ambulance company to do event stand-by EMS duty.
Safety officers at industrial facilities may also be -Bs, but they probably have some other kind of degree as well.
I'm sure any law enforcement agency, security guard company, or corrections department wouldn't mind its officers being a -B, too.