Obviously, even if you’re in your home town, the instant gratification may persuade you to use the service. It simply works by making Groupon deals appear while browsing a map. They have a distinctive “G” icon on each location icon. When you want to purchase a deal, Nokia Maps sends you to the Groupon Mobile site. Note that this is limited to the USA at the moment.
On a separate topic, Nokia also added the ability to create waypoints in-between two destinations, in case you want to plan a fun field trip. This Nokia Map update is versioned with 2.5.0.0 and should work on the following phones: Nokia Lumia 610, Nokia Lumia 710, Nokia Lumia 800 and the Nokia Lumia 900 [Official Nokia blog post]