http://el-tramo.be/blog/retjilp
Retjilp logs into your account, scans all the tweets from your following list or another defined list for a set of matching words, and retweets the ones that match (using the native retweet API).
Prerequisites of this script are Ruby and the oauth and json_pure
ruby gems (gem install <gem>).
To use this script, you will need to have registered an application with
http://twitter.com/apps to get a consumer key and secret, and fill these
values in the config file. After having changed the config file, move it
to a dir .retjilp in your homedir (i.e. ~/.retjilp).
To start the script, run
./retjilp.rb
To get a list of command-line parameters, use the --help option.
The first time the script is run, it will ask you to authorize the application in your twitter account. After this is done, the script will automatically log in the next time it is run.