http://filippo.io/Heartbleed/ is a great service to the community.
I wouldn’t recommend testing hosts againt an online tool. All you do is create a log for a security savvy person with vulnerable hosts. While not quite the same, this is similar to uploading private keys or passwords to a service to check if they are secure.
Luckily it is easy to run the software locally, as the author was so kind to provide the source. I don’t read go very well, but a cursory glance suggests that the software does what it says on the tin, so we don’t worry about it phoning home.
This is the first time I’m building a go project, so I have to install go first.
brew install go is easily done. You can get binary distributions for your OS from the go homepage: https://code.google.com/p/go/downloads/list