Speak it speaks out the contents of your emails, tweets and facebook feed. Have it read to you while you are on the road or are otherwise busy.
Speak it gives you full control. You determine which accounts you want read out to you, how many items, and how fast the speech should be.
Speak it remembers your login details so you only have to login to your accounts once, and you can hear Speak it read out the contents of your email box, facebook or twitter feed whenever you want.
Speak it also allows you to enter free text, either by typing it or copy/paste from any other application. So you can basically speak out any text you want.