Twitears-app is a project mainly written in Ruby, it's free.
A simple iPhone webapp to see where your @ replies go
This is a simple webapp, designed to be used from an iPhone, to see your mutual Twitter followers with one of your friends.
You might think of your @replies as a dinner conversation with other friends seated at the same table. Twitter assumes that, if you follow two friends, you might be interested in hearing a conversation between the two of them.
So, when you send an @reply, Twitter shows the message to the people who follow both you and the person you are messaging.
An @reply is a useful way for a group to communicate, but it's not a private message. It still appears on your profile page and in search results.
Checking to see who follows your @reply conversations can help you see how big an audience you're addressing — and that you're not accidentally spamming your other followers with a side conversation.
No. Unless they follow you, your message will not show up in their main timeline. But there is still hope. Your message will still show up under the Mentions tab, so most users will eventually get your message.
An @reply sent to someone who doesn't follow you (say, a web celebrity) is a kind of shout out to them. They might not be paying attention, but the friends closer to you (who also happen to follow that same celebrity) would hear you loud and clear.
Copyright (c) 2010 Don Cruse
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.