meteor build ../example/example --server http://example.herokuapp.com:80 --mobile-settings settings.json
settings.json
{
  "public": {
    "isMobile" : true,
    "fqdn": "example.herokuapp.com"
  }
}
I then inspect the IOS app using Safari Web Inspector and get this output:

It works fine on the web when I use meteor --settings settings.json