I would love it if someone would write a TwitterBot service. It would:

Allow you to give it the Username and Password of a given Twitter Account (let's say JSKitSupport)
Auto-follow people when they followed it
Auto-unfollow people when they unfollow it
Allow you to register one or more 'Bot Owners' (Both Twitter account and Email Address)
Forward any @replies or references to given keywords to Bot Owners
Allow bot owners to direct message it and have it relay those messages to its followers (perhaps optionally auto-append the Owner's twitter name to the end of the message)
Allows Bot Owners to direct message it commands
One of those commands could be 'd tag last' which ques up the last @reply in some sort of 'follow up' queue for the bot owners.

Can you think of any other features? Add them in comments and if I like them I will append them here!