Network Inventory of computers - Warranty Status

Dell open manage components can compile a list of service tags.  You can then export those to a spreadsheet.  Then lookup the tags.   There are no WAN harvesting agents to do this. You could try

log in on www.dell.com

go to "Your Account" -> "Find My Products and Services" ->  on drop down menu select "By Service Tag" -> enter the service tags in the box or select a csv o txt file to import a list of service tags... after that you import all the service tags, go to "My Products List" and it will show the status.

 You can also send a list of Service Tags to Support, your TAM, or to sales/warranty renewal department to get a listing of warranty details.

3rd party tool

http://spiceworks.com
http://sourceforge.net/projects/dellwt/

This handy tool determine Dell warranty information from Dell database.It can also import list of service tags from text file and then export to *.csv file.

Dell Warranty Toolkit Web Site