This is a old, buggy version of code that does weighted dollar cost averaging on both sides of the book.  This provides liquidity to the market, and with a combination of appropriate parameters (settings.rb) and careful stops, it can be profitable.  It also uses MtGox APIs, but that part should be fairly easy to interface with other exchanges.  Just set up @client using your exchange's client API in the initialize() function inside exchange_interface.rb.  The API is defined in mtgox_client.rb and the mtgox gem (https://github.com/yrral86/mtgox, forked from https://github.com/sferik/mtgox).  There are known bugs I have fixed in a private branch, as well as additional features.  I may spend some time porting those over if there is any interest.  New issues, feature requests, and pull requests are encouraged.