Incorporating live data such as sports scores, news headlines, stock quotes, and weather into your digital signage content is a great way to make your display a destination and keep your visitors entertained. Most digital signage software providers offer services or integrate with 3rd party suppliers to offer this real-time information at a cost or supply tools to incorporate generic RSS feeds.
Many end users question costs for licensed data because they can go grab similar information for free from Google or Yahoo for free. Why is this free - because those websites are trying to attract your traffic for the pay-for-clicks revenue. So while those data services may be free to you as the visitor someone is paying for you to view that data. If you read the user terms for these websites many of them specifically say it is for personal use and not allowed for public display so do your homework if you opt to go this route. Another fear with using "free" data from the web is that it could be unreliable or go away at any time. What is to prevent that website from changing their design and removing the data service you are using.
In summary using live data is a great way to make your display stand out, just make sure you use a legitimate, authorized source so you don't find yourself with blank spots on your screens or even worse a letter from the owner of that information demanding restitution.
A list of some sources of data can be found at http://creativenation.blogspot.com/2009/07/syndicated-content-news-sports-etc-for.html