If you are looking for 3rd party applications that will deal with autotrading try:
http://www.tradebolt.com
http://www.tradebullet.com
Tradebolt provides a .dll for metastock so you can send orders directly using the alert function. Disadvantage is the limitation of brokers and the reliabillity of the connection. My experience is that it is nice to play with but not stable enough to perform real trades.
Please share your experiences with us.