Tusulog complements email and more but we honestly don't think email can replaced completely. It's a simple product that sends and receives messages between people. What it does:

First it turns the basic idea of email upside down that's anybody can send mail to anybody's inbox. With Tusulog messages from people you don't know goes to Public Pipe and also you can disable it altogether. BTW, your friends can send to your inbox directly.

Second with email you apply the filter after getting the message. With Tusulog you apply the filter (pipe) before. PG, taking your example literally: You create a TODO Pipe with public_key THEPUBLICKEYOFPGSTODOPIPE. You give this public_key to people you want. They can send message to that pipe in other words they can put a task into your ToDo list. They can do it using Tusulog UI or Tusulog API.

edit: added linebreaks

I'm the co-founder of Tusulog ask me anything.

bdfh42: you know it's just like that always. Chicken-and-Egg. Maybe you can open another account to test or add me as friend http://tusulog.com/people/mehmet we can exchange a few.

kaolinite: honestly you should have a few friends over there to really decide you want or not. A reason maybe as a user you've absolute control of your inbox.

Why would I sign up without having a clue what it does? I already have a free service for sending and receiving messages - tell me why I want your service.

The (very little) information provided implies that this only works for communicating with existing users - so a bit like the first person to pay for a telephone to be installed - who are you going to call?

A good demo would help - perhaps some legacy support to get things moving?

Really not clear what this is...