I needed something like this for my work (@appadvice) and couldn't find it so I made it on my own :) and just posted in on the App Store. What StreamBoard does is plugs into Twitter's streaming API for any keyword you want, and display the results in real-time in a table view.

You can filter the results too, which is quite powerful if you track news things like, everyone who says iPhone in a tweet that has more than 500 followers and speaks english and includes a link in his tweet. It also does location-filtering to some extent.

I used to use Datasift Beta to do this, but now they want a LOT of money for it, so I made my own filtering engine in obj-c.

I literally learnt Obj-c and made it in about 14 days, so the UI is a bit rough. The engine however should be rock solid. If you have time to try it for me, here are some promocodes:

R6HR4N6MPAHM 4E7X4JA6YNEF YAJNWEW3AX6N 7KMH9MA9P6TR F9K6W36KXNX3 LNHLR47HWH6Y HP7A4FE4YY4J 6PMAM6XY94ET K43FJPHMKME7 W4JXA6PWPKMW

Try it out, and let me know what you think!