Hoptoad meets Sinatra.

    _____                                ,
   /     \______                         |\        __
  | o     |     \____                    | |      |--|             __
  /\_____/           \___                |/       |  |            |~'
 /                       \              /|_      () ()            |
|_______/                 \            //| \             |\      ()
  \______   _       ___    \          | \|_ |            | \
        /\_//      /   \    |          \_|_/            ()  |
       // //______/    /___/             |                  |
      /\/\/\      \   / \ \             @'                 ()
                    \ \   \ \      
                      \ \   \ \    
                        \ \  \ \   
                         \ \ /\/\  
                         /\/\

How?

require 'sinatra/toadhopper'

set :toadhopper, :api_key => "your hoptoad API key", :filters => /password/

get "/" do
  raise "Kaboom!"
end

error do
  post_error_to_hoptoad!
  "Ouch, that hurt."
end

Install it via rubygems:

gem install toadhopper-sinatra