I see zbxapi.rb can be run as a command-line program. However, when I try it throws an error (see below).
Performing login
/Users/foo/.rvm/gems/ruby-1.9.3-p0/gems/zbxapi-0.1.369/zbxapi.rb:101:in `initialize': undefined method `+' for #<ZabbixAPI:0x00000104857988> (NoMethodError)
from /Users/foo/.rvm/gems/ruby-1.9.3-p0/gems/zbxapi-0.1.369/zbxapi.rb:102:in `new'
from /Users/foo/.rvm/gems/ruby-1.9.3-p0/gems/zbxapi-0.1.369/zbxapi.rb:102:in `initialize'
from /Users/foo/.rvm/gems/ruby-1.9.3-p0/gems/zbxapi-0.1.369/zbxapi.rb:344:in `new'
from /Users/foo/.rvm/gems/ruby-1.9.3-p0/gems/zbxapi-0.1.369/zbxapi.rb:344:in `<top (required)>'
from /Users/foo/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
from /Users/foo/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
from /Users/foo/.rvm/gems/ruby-1.9.3-p0/gems/zbxapi-0.1.369/api_classes/subclass_base.rb:27:in `<top (required)>'
from /Users/foo/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
from /Users/foo/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
from /Users/foo/.rvm/gems/ruby-1.9.3-p0/gems/zbxapi-0.1.369/api_classes/application.rb:27:in `<top (required)>'
from /Users/foo/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
from /Users/foo/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/site_ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
from /Users/foo/.rvm/gems/ruby-1.9.3-p0/gems/zbxapi-0.1.369/zbxapi.rb:48:in `<main>