sim.bz is a simple domain to help with local development. You can use any subdomain and it will point to localhost:

          pancakes.sim.bz resolves to 127.0.0.1
      french-toast.sim.bz resolves to 127.0.0.1
strawberry.waffles.sim.bz resolves to 127.0.0.1
    

When you're ready to share your site you can use an ip address in the domain (just like xip.io)

          pancakes.10.0.0.1.sim.bz resolves to 10.0.0.1
      french-toast.10.0.0.1.sim.bz resolves to 10.0.0.1
strawberry.waffles.10.0.0.1.sim.bz resolves to 10.0.0.1