NOTICE: No longer available. Many thanks to all who tried Fraser the Bot!

   Telegram

https://telegram.org/

   Chatting with Fraser

Telegram allows bots for one-on-one and group chat. On the Telegram menu, select Contacts, then click the search icon . Start typing fraserthebot and Telegram will find him for you. Click on Fraser the Bot in the search results to start a chat.

   Group chats

First, you will need a group with one or more of your Telegram contacts. Then, from within that group chat, click in the center of the top title bar, where it shows your group name and number of group members. (That little trick wasn't obvious to me.) You get a nifty new screen with some useful details and settings for your group. Click on "Add member", and then use the search function just like the previous instructions for a private chat with Fraser.

If you want Fraser to completely ignore a message, start the message with an 'x'. For example:
x How's your weekend been?
X I'm stuck, any ideas?