twitter bot that auto replys to keywords

Anybody know any programs that automatically reply to a certain keyword on twitter without getting banned.

eg. I sell soap and you post

"great day in the bath but shame about my soap"

id want to automate a tweet to them saying - buy soap here ..... link


Also is there a way you can only send it to people NOT following you (so you dont spam your friend list)

thanks

85 posts and you haven't heard of Tweet Attacks?