the steps your script would have to take are as follow:
1: retrieve your ID from
https://api.twitch.tv/kraken/channels/yourchannel2:check
http://tmi.twitch.tv/hosts?include_logins=1&target=yourID every minute or so to see who hosts you
3:strip the hosting usernames
4: if there is no cache, then cache the names. Else match the cache with the newly collected usernames
5:if new names, echo to chat
something like that, maybe.