Persistent

irb-history-server stores its history in YAML in a file of your choice (the
default is ~/.irb_history).

Shared

Load the irb-history client in your ~/.irbrc, and you'll instantly have
access to the irb-history store. Every line you type is sent to the server
and will appear in other clients' histories immediately.

Because irb-history uses DRb, you can share your history with other IRB
sessions:

    * on the same computer
    * on other computers on your local network
    * on computers connected to the Internet (fun, but not recommended :))

Installation and usage
----------------------
It's a simple process:

   1. Install the gem.
        $ gem install irb-history

   2. Start a history server listening on 127.0.0.1, port 26501 (see the
      irb-history-server documentation for more options).
        $ irb-history-server -d

      Note: If you wish to use irb-history on a network, you'll need to
      pass the -h flag with an appropriate address to listen on.

   3. Add three lines to your ~/.irbrc.
        require 'rubygems'
        require 'irb/history'
        IRB::History.start_client

      This connects to the history server on 127.0.0.1, port 26501. If you
      need to specify a different host and/or port, just pass a DRb URI to
      start_client. For example:
        IRB::History.start_client 'druby://galt:4000'
      connects to the history server on host galt, port 4000.

Source code
-----------
Check out the darcs repository:
  $ darcs get http://dev.conio.net/repos/irb-history
RDoc documentation:
  http://irb-history.rubyforge.org/rdoc/

irb-history is freely distributable under the terms of a MIT-style license.
Enjoy!

I'll be testing this out asap!