Twitterhawk is a service that flags tweets based on your keywords, and allows you to auto-respond - or respond later, by hand - with your marketing message.
From the home page:
TwitterHawk is a real time targeted marketing engine that will find people talking on twitter now by your chosen topic and location, allowing you to really hit your target mid conversation with ease.
It will periodically search twitter for you and either auto-reply or generate a list of matches for you to respond to or reject from your twitterhawk account.
Seems the best thing to send in your tweet would be a link to your site or service.
Here's a use case from their website:
Let's say you just opened a new coffee store in Queens and wanted to let people know about it. As part of your advertising efforts, you could setup TwitterHawk to search for things like "coffee near:Queens within:8mi" (of course you could simply search world wide if you are global).
We would then periodically (at a frequency determined by you) find twitter posts that mentioned coffee by users that are actually located within 8 miles of Queens such as
'@cracksh0t Oh I could really go for a coffee right now' or
'@loxly Coffee... my one true love'
Depending on how you set your search up, the system will then either send the response automatically right then, or it will add it to your matches list for you to check over and confirm.
Should there be a match for coffee on something like '@coffeeh8r I cannot stand coffee!!!' you can simply remove this from your matches list.
Twitterhawk can track how many links you send and how many of those result in click-throughs - sort of a CPC model for tweet-marketing.
So - is this spam? Or smart context-sensitive communication?
Twitterhawk's services page