While this only mentions native applications, the same could be done for web apps:

  <meta name="apple-mobile-web-app-capable" content="yes">
  <meta name="apple-mobile-web-app-status-bar-style" content="black-translucent" />
  <style>
    html {background-color:#000;}
    body {background-color:#fff; border-radius:6px}
  </style>