Here's a short explanation of what each instant messaging service currently offered actually does.

Reminders
The reminder service is designed much like a calendar where you set events to be reminded about, and the service will send you a instant message reminding you of that event.

RSS Feeds as instant messages
Give us an RSS feed (or two, or three... ) and we'll send you a heads-up when your selected feeds are updated. Quite handy on forums we use this one ourselves.

Block Checkers
Do you suspect someone has blocked you? Find out!
This will only work if the person who you suspect has blocked you has privacy turned off.